Category Archives: Up On ARs

Trigger Installation

The Basic Format.

It’s unlikely you’ll be installing a stock trigger in your rifle, but most aftermarket triggers still use the same essential parts in the same ways as the GI system. If you take your GI parts out for a clean and lube, reinstall them this away.

There are two pins—a trigger pin and a hammer pin. With exceptions usually encountered only in aftermarket sets, they are the same. Unless it’s Colt-brand, trigger and hammer pins are 0.154-inch diameter. Colt takes 0.173.

This is, or should be, a hand-done installation. One tool you do not need is a hammer. If a pin won’t fit into its receiver hole using finger pressure alone, either pin or hole needs a close look and perhaps an edge broken, or better alignment from you. Do not tap-hammer these pins! One tool that really helps is a correctly-sized (0.154 inch) punch used as an assembly slave, and mechanic-style gloves make the hammer’s installation less hurtful.

Test fit the pins. They should press into place through the receiver holes and the trigger and hammer should rotate freely on the pins.

Grease the pin holes on the hammer and trigger. This especially helps overcome the resistance from the hammer pin fitting over the J-spring within the hammer body.

Whatever you do, do not let the daggone hammer fall forward against the lower! The lower receiver can and will crack if the hammer hits it full-force. A well-positioned piece of leather or wood works when doing your tests and checks.

Place the trigger into the lower making sure the return spring stays in position. The disconnector spring is in its place. The tail of the trigger assembly goes under the safety bar, and the safety selector should be in the “FIRE” position.

Set the disconnector into its place and line up the holes. An assembly punch makes this easier. Push the punch in from left to right (because the pin comes in from right to left). Run the punch into the trigger but not into the channel where the disconnector sits and then position the disconnector, then push it through. The notch should be right over the disconnector spring. Push the disconnector down so its hole lines with the trigger pin hole.

Start the trigger pin from right to left, ungrooved end first. If you’re not using an assembly punch, use the trigger pin in the same way: push the pin into the trigger but not into the channel. Put the disconnector into place and push down on it to get alignment. Continue on until the pin enters the receiver hole on the left side of the receiver and comes to flush with its exterior surface. Done. Check that the trigger moves freely and the disconnector is free to rock to and fro. If it won’t, make sure its spring is seated.

The legs of the hammer spring should be pointing toward the rear of the receiver. Both legs of the hammer spring have to be on top of the trigger pin. One leg fits into the groove on the right side of the trigger pin to keep the trigger pin from slipping out. This is a strong spring. I use an assembly punch run through the left side of the receiver to position the hammer in place, and then the pin itself installs using the punch as a slave to guide it. To get the hammer in position, push down and somewhat forward on the hammer to compress the spring and lower its hole into alignment with the receiver holes. It will want to push back and up. The action that prevents it from winning this battle is a sort of pseudo-cocking force applied to the hammer with your fingers. The hammer is pushed down first and also then forward to position the pin hole. Keep pressure down on the hammer to get the pin fully through the left-side receiver hole.

Now that it’s all together, it’s a system and it all has to work.

The safety switch should only move from position to position when the hammer is cocked. When the hammer is forward, it should not go to the “SAFE” position.

Cock the hammer. Pull it back and push it down until it clicks into place. Rotate the switch to “SAFE” and pull the trigger. Pull it hard. Hammer should not fall. Rotate the switch to “FIRE.” Hammer should not fall. Pull the trigger and the hammer should fall.

Do not fire the rifle unless the disconnector is functioning.

The disconnector prevents the hammer from falling until the trigger is released forward enough to “reset” the sear and hammer hook or notch.

Cock the hammer and then release the hammer forward by pulling the trigger. Keeping the trigger held fully to the rear, cock the hammer again.

Now, just as slowly as you can, release the trigger forward. The hammer should “jump” up as it’s handed off from the disconnector to the trigger sear. I redo this check on an assembled rifle by letting the bolt carrier slam home to better duplicate firing. Then, of course, come range tests.
By Glen Zediker

The trigger pin installs from right to left (above), ungrooved end first. Glen uses an assembly punch. If you don’t, push the pin into the trigger but not into the channel. Put the disconnector into place and push down on it to get alignment. Continue on until the pin enters the receiver hole on the left side of the receiver and comes out flush. Done. Check the trigger moves freely and the disconnector is free to rock to and fro. If it won’t, make sure the disconnector spring is seated. The hammer spring (below) is strong. To get the hammer in position, push it down and somewhat forward to compress the spring and lower its hole into alignment with the receiver holes. It will want to push back and up. To prevent it from winning this battle, apply a sort of pseudo-cocking force to the hammer with your fingers. The hammer is pushed down first and also then forward to position the pin. Keep pressure down on the hammer to get the pin fully through the left-side receiver hole. An assembly punch run through the left side of the receiver to position the hammer in place really helps.

Here’s how the springs should look. The trigger-spring loops just snap fit into place over the bosses on the trigger. Note the orientation. The hammer spring installs in the same way. Orient the piece correctly and then snap one spring loop over one side and the other spring loop over the other side. The little feet are pointing, well, like little feet would point, and the square portion of the wire is under the sear bar.

OK, you’ve gotten your lower apart and this what you have. If you can reinstall all this, then most other available triggers will fit into place for you also. Don’t expect a good pull from a stock system. Engagement surface polish and lighter springs are about the only ways to make a standard trigger pull better. The pins are KNS-brand pins, correct and true. The same can be said for most pins supplied with aftermarket triggers, but a set of KNS will improve whatever a trigger pin set can improve. These pins always install from right to left, ungrooved end first. (Some aftermarket trigger systems and pins are an exception to this rule.)

Always (always) check for disconnector function (above). With the hammer fully forward and the trigger pulled fully to the rear, cock the hammer with the trigger held steady. Then, slowly, release the trigger forward. The hammer should “jump” up and hold when it’s handed off from the disconnector to the sear. Whatever you do, don’t let the hammer hit the receiver with full force. It will crack. Don’t confuse the bolt-catch-plunger spring (below, right) with the disconnector spring. They are just about the same size, but the disconnector spring has a larger end. This larger end goes into the recess located in the channel on the trigger body. Some GI triggers have two recesses. If so use the front hole. Put the spring into the recess and then push it fully home. Push it hard. You will feel it seat. Glen uses an assembly punch.

Shameless Self-Promotion

The preceding is a specially adapted excerpt from The Competitive AR15: Builders Guide, a book by Glen Zediker and Zediker Publishing. For more information, check out www.ZedikerPublishing.com or call (662) 473-6107.

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The Barrel Install

You Have The Tools, Now Here’s How.

After we got the tools in order last time, using them to install a barrel is actually pretty easy.

An AR-15 barrel assembly is a slip-fit into the upper receiver. The barrel extension fits into the opening in the upper and there’s a pin that indexes it in place. A barrel nut then gets turned onto the threaded area that surrounds the opening in the upper receiver and this nut is tightened to secure the works. The nut bears against a flange or shoulder on the barrel extension. The barrel nut has 20 dished cutouts or holes that align with the gas tube hole in the upper receiver. Here’s the thing: one cutout has to align exactly. The smallest amount of contact between the gas tube and the barrel nut can diminish accuracy. By the way, barrel nuts are all essentially the same, whether standard configuration or aftermarket.

Any and all ready-to-go barrels I’ve seen or heard of will unpack with the barrel extension in place. If it wasn’t there then the barrel would be in no way ready to go. Installing an extension onto a barrel blank is well beyond the scope of this article—it’s all machine-shop ops.

Armorer’s manuals call for an installed barrel-nut torque specification that makes it sound like it’s all easy peasy. It’s not always. Most call for 35 foot-pounds of torque. That is a minimum necessary for retention, and then one of the barrel nut holes has to line up. That’s the trick.

The torque specification, then, is really a minimum because it’s likely (highly likely) to take more than that to get the job done. The best thing that can happen, aside from perfection, is having the hole be just a little off such that a little more tight gets it perfect. The worst thing is when it’s sitting about halfway on the other side of aligned and will take dang near another whole hole’s worth of rotation to align with the next available cutout opening. If that’s what it is, then that is also what has to get done. It will take some force. So don’t put the barrel on at less than 35 foot-pounds of torque, and also don’t be surprised if it takes 60 or better to get alignment. It takes what it takes. Now, there is an easy way to make it work—remove metal from the cutout on the barrel nut to attain clearance. I think if there is an excessive amount of torque needed to get alignment, that’s a sane way to proceed, as long as no more than a scant amount is impeding. Use a high-speed hand grinder, like a Dremel tool.

To gauge gas-tube clearance, I use a gas tube alignment tool, which is really just a short piece of round stock that replicates the gas tube. Insert the tool into your bolt carrier key, insert the carrier fully, and check clearance of the gage around the barrel nut cutout. You can make a tool from an old gas tube, or get a sano version engineered for the task.

Take the nut (above) to tight, loosen, and to tight again two or three times. This helps to “seat” the surfaces. A gas tube alignment tool fits into the bolt carrier key (below), and the carrier is then inserted as normal into the upper. Be very critical of clearance, and do this as many times as it takes to get a perfect gap. The final check comes on gas tube installation. The tube should rattle. This tool is from Brownells.

This isn’t fully necessary, but Glen always glues the extension into the upper for a “precision” rifle, such as a competition arm or varmint gun. The glue helps take up some of the gaps that result from the slip fit. Glen use Loctite “red.” Be warned that it will take a lot of heat to remove this bond.

Use antiseize, like Loctite C5-A, on the receiver threads and barrel nut joint. In case there’s a lot of torque necessary for a particular installation, this is insurance against galling, which means the nut won’t continue to progress, which can lead to cracking the upper.

Barrel installation is really all about alignment of the gas tube. Don’t rest until the gap is perfect. Or cheat and make it perfect. Just as long as it’s perfect, it’s good enough. That’s a joke. But true.

Begin Here

To start the process of installation, fit and unfit the barrel nut at least a couple of times by hand to get the threads chased. Then apply a good antiseize compound to the receiver threads. This is a product engineered to ease the stress on such an operation. It’s not oil, but a copper-based lubricant. It will in no way encourage a barrel to loosen. It’s insurance against galling, which can lead to cracking. And, yes, upper receivers can crack during this operation. Evermore reason to select a quality go-between to secure the upper into a vise, as discussed in the July issue (it’s online at www.gunsmagazine.com/digital-editions).

After applying the antiseize, use a breaker bar or torque wrench on the barrel nut to fasten down the barrel to either tight snugness or the recommended torque. If you’re using a torque wrench, switch to the breaker bar to loosen the barrel. As discussed last time, don’t use a torque wrench to loosen, only to tighten. Torque it down, back it off. Repeat one or two more times. Do this to seat the barrel in the receiver extension with the idea of overriding and hopefully eliminating irregularities in this area.

I use high-strength glue to fix the barrel extension into its sleeve in the upper. Right. That means it’s not going to come back off without heat. It also, however, often improves the fit in this area, which, keep in mind, is a slip fit. Some uppers and extensions will combine to create a gap greater than others. The glue is not at all necessary to have a fully functional AR-15 that probably will shoot just fine, but it’s a little step someone looking for the best results really should take. Degrease all associated surfaces before applying the glue, and don’t do it until after test fitting. You’ll have plenty of time before the glue sets.

If the barrel nut gets over-tightened out of alignment, bring it back where it needed to be without worry. As long as minimum torque was attained prior to, there’s no harm in backing it off a tad, and there’s also going to be no other option. Go carefully though. Ultimately, it’s the gas tube that’s installed in the rifle that needs attention to the quality of its fit. The alignment tool just gets the holes to share centers.

Point is—and this is just it—there has to be perfect alignment. Has to be. Work at it as long as it takes. If you don’t, the rifle is likely not to shoot too well. The gas tube should rattle when the bolt is in battery, that means fully forward, locked up. There should be no displacement of the tube in any direction when the carrier key is engaged and disengaged as the carrier moves forward and backward. Feel, listen, look. I place my index finger on the gas tube and then run the carrier in and out. You can usually feel the tube shift as the carrier key engages and disengages the gas tube. If the gas tube is binding it will displace the carrier in the upper. Even just a little has a big influence. I’m convinced that the root reason for the accuracy of the AR-15 is from its “floating” lock up.

If centers are centered and there is binding in the gas tube, then the tube itself has to be bent. Bending a gas tube isn’t easy. It’s stainless steel and will snap with virtually no warning. Rubbing the area of the tube where you’re bending back and forth over a wooden dowel while applying steady pressure helps result in kink-free displacement. Don’t get greedy! If the gas tube rattles, you are good to go.

Information in this article was adapted from The Competitive AR15: Builders Guide, published by Zediker Publishing. Glen is a card-carrying NRA High Master earned using an AR-15 service rifle. For more information, including many downloads, check www.zedikerpublishing.com.
By Glen Zediker

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Barrel & Upper Work

Some Tools Are Essential For Assembly.

There is a huge interest in folks wanting to assemble their own AR-15s. I characterize the efforts as somewhere between changing a lightbulb and installing a garbage disposal. Depends, of course, on the job at hand. To build an AR-15 you’ll need to install a barrel. That would be a long article, so here I’ll take a look at the tools you need for this project. As with any kind of mechanical endeavor, tools really matter to your success.

A good vise is absolutely necessary. You’ll need a heavy-duty model with at least a 4-inch jaw opening to hold things like receiver blocks and fixtures and barrels. Do not scrimp on the main vise.

My favorite is the Brownells Multi-Vise. This truly well-engineered tool is worth its cost. It can easily swivel and allows for vertical or horizontal jaw orientation. Again, you might not think it’s worth its cost until a lower quality vise lets you down. Of course, Brownells has a custom-fit set of pad inserts available for it too, and those are recommended.

The most important tool in your shop is a quality vise.
Without one, you’ll start with a handicap.

Clamps And Wrenches

To do any barreling work, you’ll need a means to hold the upper receiver securely, and without damage. Receiver blocks come in two essential formats. There are blocks that fit into the upper, and that style is my preference. The one I like best uses takedown pins so it is, in effect, like clamping the lower with the vise. Derrick Martin gets credit from me for this invention. Others are “clam-shell” parts that encase the upper and also fill the space where the bolt carrier normally occupies. There’s really no difference in how well they work.

The big difference, however, and pay close attention, is that the clamshell-style blocks are a skin-fit to an A2-configuration upper, whether it’s a flattop or carry-handle. That’s all they’ll work with. If you need to hold an upper that’s dimensionally different, such as one of the DPMS “competition” style uppers, and other unique styles, they won’t work at all.

Holding the barrel itself, normally using a pair of barrel vise-jaw inserts, is a popular way to secure an upper, but I so-o-o do not recommend it. The note against holding the barrel and for securing the upper is that the indexing pin on the barrel extension that fits into the upper can lever against its slot when the barrel, not the upper receiver, is held in place. This can elongate the slot. Barrel clamping block sets are numerous and it’s hard to find any that actually work all that well.

This is especially true if you’re installing a barrel that’s even a little different dimensionally than issue-spec standards (which is what the vise inserts are engineered around). Rosin can help stiffen the grip. It will take a good deal of pressure to secure a barrel from slipping when an inordinate amount of pressure has to be applied to a barrel nut to align a stubborn gas tube hole. Don’t worry, by the way, you’re not going to bend or crush a barrel. I don’t like clamping the barrel because of what was just said. It also mars the fool out of them, no matter what I’ve tried.

I do, though, think such appliances are handy for installing, or removing, muzzle attachments and securing a barrel for a chamber polish or for thorough cleaning. Especially in an op like removing a flash-suppressor, I prefer clamping the barrel itself rather than using an upper-receiver clamp to secure the works. There’s a lot of leverage working all the way out at the end of the barrel and clamping the barrel itself takes that advantage away from what might otherwise be directed against the upper receiver.

Holding the lower is painless and downright convenient with one of the blocks that substitutes for a magazine. There’s little stress ever levered against a lower that in any way compares to that raged against an upper during a barrel or fore-end tube installation. They are also daggone handy for cleaning, sight installations, and general maintenance work. I have one clamped in a vise most all the time.

To install a barrel, any barrel using virtually any retention means (meaning free-float tube or not), you’ll need a specialty barrel nut wrench.

The “armorer’s combo-tool” standard has three prongs that engage the scallops in a barrel nut. This will work with any barrel nut arrangement that’s configured like a standard nut, including those on most free-float tubes. I prefer the “full-round” style that engages each and every scallop. This style wrench, however, has to be able to fit over the muzzle and be brought back to the barrel nut, so can’t be used if installing a barrel that already has the front sight housing or handguard cap affixed.

I do not recommend purchasing one of the multi-purpose tools that has its own handle and is a self-contained tool. (By the way, the reason I’m referring to these as “multi-tools” is that they have cutouts that fit, sort of, the receiver extension and flash suppressor nut.) The variety of barrel nut wrench you need has an attachment for a 1/2-inch drive, into which goes a wrench handle, and now we’ll talk about those.

Never, ever vise-up an upper without either of these devices. The “clamshell” type (above) is the most popular and is a skin-fit to an A2 upper with or without its charging handle. Glen prefers a style that fits exactly inside the upper receiver (below). The upper receiver can’t move using this block. The limitation of the clamshell style is that it only fits an A2, not any of the “other” configuration uppers, such as the newer billet-made uppers. In other words, the clamshells works off the exterior and the insert works off the interior. The interiors don’t change.

Torque Wrench

A breaker bar and torque wrench are important tools, especially for those inexperienced with barrel installations. If you don’t have a torque wrench then you’re guessing, but after a few installations you’ll be guessing on the safe side of error. The reason for the breaker bar is because rumor has it that a torque wrench should only be a one-direction tool: it’s only used to tighten, never loosen. I couldn’t really confirm that rumor, even after asking a few race mechanics, but let’s assume it’s true.

These tools can come from any good mechanic’s supply. I like torque wrenches with longer handles because sometimes the amount of force needed for a barrel installation gets on up there and the longer handle makes subtle shifts toward tight easier to control. The breaker bar is therefore only needed to loosen this nut.

As mentioned, the combination tools have additional cutouts to fit the receiver extension tube and muzzlebrake nut, but the fit is usually poor. It’s far preferable to have handy a good quality adjustable wrench, or better still, open-end wrenches that are correctly sized for these fasteners.

Information in this article was adapted from The Competitive AR15: Builders Guide, published by Zediker Publishing. Glen is a card-carrying NRA High Master earned using an AR-15 service rifle. For more information, including many downloads, check www.zedikerpublishing.com.

Barrel clamps are not to be used for installing barrels, says Glen, but do come in handy when it’s necessary to work on the barrel itself. Rosin helps increase the grip if necessary. Always clamp the “fat” part of the barrel.

Here’s a barrel nut wrench (above), when Glen can use it. This grips the barrel nut scallops full around but only works when it can be slipped over the muzzle. When a front sight is already mounted, then something with an open end is necessary such as the “standard” armorer’s wrench (below). There are others, but the wrench needs the 1/2-inch drive cutout for use with a breaker bar and torque wrench.

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By Glen Zediker

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Get Out!

Extraction & Ejection.

An “extractor” is there to pull a spent case out of the chamber and the “ejector” is there to toss it out the ejection port. When they don’t then they need fixing. Extractors first.

Some seem to have decided that increasing the spring pressure or tension against the extractor is the solution to all problems. Nah. A whole lot of extraction problems have little to nothing to do with extractor function.

I prefer to start with the simple view first. That’s the first step to solving a function problem. Right, make sure it’s plugged in before calling an electrician. Extraction problems come when the round doesn’t want to come out of the chamber, and they are augmented by cases sticking to the chamber walls, and roughness is a leading contributor to reluctance to release. A telltale sign is the extractor leaving its impression on the case rim, or even bending or tearing a chunk out of it. That means the extractor is trying just as hard as it should, but it’s tugging on an immovable object.

The first thing then is to clean the chamber! If that’s not been a habit, then there may be residual roughness afoot. Usually this is plain old gunk, but under some circumstances there can be corrosion. Note that a culprit can be residue from a potentially corrosive-inducing bore cleaning solvent that’s leeched its way onto the chamber walls. Again, don’t neglect to swab and protect the chamber just as you would the barrel bore. All chambers in all rifles I own have polished chambers, bolt guns too. Shiny patches on spent cases are an indicator of sticking points in the chamber.

AR1

Dirty chambers contribute to extraction ills, as will—not can—rough chamber walls. Glen polishes his. Clean a chamber with a nylon .357-caliber pistol brush (above), and then wrap it with a patch to finish. Below is an extractor spring Glen pulled from a new bolt. It had one of the phenolic inserts already in it. Middle is a “D-Fender” insert. This goes over the stock spring and increases tension about 400 percent. Inserts can be a fix, but not really a cure. On right is a chrome silicon spring from Superior Shooting Systems. It’s about a 100 percent increase compared to a stock spring. Do not run the CS spring with an insert or D-ring. Brownells has all.

AR3

Sizing

If you’re a handloader, as long as you used a full-length sizing die, case sizing really shouldn’t influence extraction. If there’s not been “enough” case body sizing, that usually creates feeding problems. The choice of brass might factor, though. The softer the brass alloy is, the more it swells and the “stickier” it gets. No semi-automatic should be run with soft brass. Harder composition cases expand essentially the same amount but contract a little faster and a little more, and that’s the key. Brand names? Nosler, WW Commercial, Lake City with ’91 or newer on the head.

The stronger the load the more the chamber contributes to extraction difficulties. When there’s an overage of propellant gas passing through the system, coupled with its symptomatic increased rapidity of bolt unlocking and rearward travel, what is really happening is that the case is still expanded against the chamber walls when the extractor tries to yank it out. If it’s trying to yank a still-expanded case, then a relatively rough chamber makes it more reluctant. Even in a mirror-finished chamber this can be a problem, and abating this condition comes, most easily, from realizing that there’s too blasted much propellant in those cases. Additional (big) helps come from delaying bolt unlocking.

As said, a case is supposed to swell up inside the chamber. Brass alloy expands and then contracts, and, since we’re talking about the firing process, all this is taking place in scant milliseconds. Delaying unlocking even a little bit, and along with it the employment of subsequent and sequential machinery that extracts the spent case, gives more time for the case to shrink from the chamber walls. Out she comes! A telltale on this problem is extraction with a normal-pressure load and not with higher-pressure loads.

Other articles I’ve done have offered means to delay unlocking, but without gas system overhauls, adding some weight to the bolt carrier or running a stouter buffer spring, or both, work wonders.

Let’s now say that none of those things are contributing to a rifle’s extraction problems, or, even if they are, there’s an absolute reason that a load has to function in the rifle. Now we can talk about extractor pressure. The extractor spring pushes the extractor in toward the bolt, holding it against the case. Extra spring tension makes the part grip more tightly and be less resistant to losing its hold.

ar bullet

If you see anything like this (above), it’s not the extractor. It’s the load. This is a well-over pressure NATO round fired in a .223 SAAMI-spec chamber. Now, these didn’t extract, or not always. Look closely on the left edge (below) and you’ll see a warp in the rim from the extractor trying to keep hold, but then losing its grip. And, no, a stronger hold on the rim is not the best answer. Not on this one!

ar bullet 2

D-Ring Inserts

There are gizmos designed to increase extractor tension. Specifically, these are the “D-ring” inserts that go in with the stock spring. They are made of phenolic (fancy plastic) material. They increase load, but too much. I think it’s a better trick to replace the stock spring with a better spring. I run chrome silicon extractor springs as a habit now. I can’t say I would have case removal problems without them, but I don’t have any problems. This spring material is unaffected by heat, doesn’t work harden, and doesn’t change function for a good 10 times longer than stock. It’s common enough for music wire springs to just break in full-autos.

When a round is chambered, the extractor has to “snap” into place by sliding over the edge of the case rim. When there is more pressure to overcome due to excessive extractor spring resistance, there’s also more pressure put against the case head as the bolt is moving forward to lock down. This extra resistance from the extractor hitting the base of the cartridge can push the case way too hard into the chamber, which really means too far, in effect. This is one contributor to the reason we can often measure reduced cartridge headspace after chambering and extracting a loaded round for a gage check. The case shoulder can be set back a little from this resistance before the extractor clips over the case rim and locates the round on the bolt face where it should be.

I don’t know that this just kills anything, but it’s like taking a pin punch to the case after it’s chambered. Can’t be good. Some like to put a polish on the leading edge of the extractor to reduce friction. Good idea. Another good idea is a polish right in the extractor groove (but don’t dull the edge). This area at the least should be smooth, clean-edged, and burr-free. Too much friction makes it harder to pivot on the case rim.
Ejectors next time.

Information in this article was adapted from The Competitive AR15: Builders Guide, published by Zediker Publishing. Glen is an NRA High Master and earned his classification in NRA High Power Rifle using an AR-15 Service Rifle. For more information, check www.zedikerpublishing.com.
By Glen Zediker

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Guns Magazine March 2013

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Let’s Look Inside

Case Sizing Part II

Last time, we talked about resizing a spent cartridge case for best reuse in an AR-type firearm. The focus was on the outside of the case. This time we’ll talk about the inside, the case neck area. Options matter more than you might imagine. Before talking options, the first step is understanding the essence.

There are two diameters on a case neck, both matter. Inside diameter and outside diameter. On firing, the case neck will expand to fit the limits of that area in the rifle chamber. For safety’s sake, most factory chamber neck areas are fairly generous in size (compared to what we might get away with in a custom chamber and consistent brass). That is done to accommodate a wider variety of cartridge case specifications. Not all case neck walls are the same thickness, so not all neck diameters will be the same. There has to be room for the case neck to expand to release the bullet. If there’s not, then pressures can escalate.

In resizing, the case neck gets its outside squeezed down and then its inside gets opened back up.

Most conventional sizing dies are going to take the fired neck outside diameter down a significant amount. These dies incorporate an expanding appliance, usually called a sizing button (some, me too, call it an “expander”) that comes back through the case neck when the case is withdrawn from the die. This is affixed to the decapping rod. The button diameter determines the inside case neck diameter, and also then the outside neck diameter.

It’s inside diameter that’s important. Inside diameter determines case neck constriction, which some call case neck “tension,” and that matters a whole lot. It matters to safety and accuracy. It’s the difference in diameters of the bullet and the inside case neck. For a semi-auto it should be at least .003″. Less than that and retaining the bullet against movement prior to firing can be a question. This movement can be induced through inertia or impact. Much more than that (more than .005″ difference) and then the bullet may get its jacket damaged on seating, as well as having the bullet become an unwanted contribution to the sizing operation. If there is excessive seating resistance, the case shoulder may get additional setback.

Some, me included, are concerned with the amount of down and up in the sizing operation. No doubt, more sizing “works” brass and shortens its life. There are sizing dies that feature changeable bushings to specify the amount of outside case neck sizing. It’s possible, certainly, to use this to reduce the amount the expander opens up the neck.

I really don’t recommend bushing dies for semi-autos. One of the main points against them is that they don’t size the full height of the case neck. Not sizing the full neck tube is a contributor to the influence of the case neck “doughnut” I talked about in the October 2008 issue. (In case you missed that, this is narrow elevated ring of brass that increases constriction by reducing the inside neck diameter. It’s like rolling an O-ring down into the case neck, stopping it right at the case neck, case shoulder juncture.) As I hope makes sense, it’s also for this reason I don’t recommend sizing a case without a sizing button in place. This is easily possible with a bushing die. Squeezing down the outside diameter of the neck without opening its inside back up will, I promise, form a doughnut. The sizing button reopens the neck inside and helps alleviate the effects of this condition. It can also influence accuracy, in a bad way, contrary to the intentions of following this procedure.

AR 1

Exaggerated, of course, but because wall thicknesses vary there literally
can be two different centers in a case neck with non-uniformed walls.
Which influences depends on whether the case neck was last sized
inside or outside. If you don’t neck-turn cases, it should be inside.

Neck Centers

In effect, there are two centers on a case neck, one outside and one inside. The inside matters most because that’s where the bullet is, and that’s what it gets seated into. To see how literal this is, sizing a case with no expanding appliance, such that only the outside wall is touched, and then running it on a concentricity fixture will almost always show zero to very little runout. Take the same case and size it using the expander such that the inside neck wall is the last thing touched, and another check with the fixture will likely then show runout. Expanders get blamed but the bigger thing is that it’s only pointed out neck wall thickness inconsistency.

If case neck walls aren’t uniform in thickness, then whatever amount of inconsistency there is displaces either center. If we want the inside wall center to be in the center, then an inside expanding appliance should be the last sizing tool used on the case neck. The only case necks that respond better to no inside sizing are those on uniformed brass, and specifically that means they’ve had their necks outside-turned so their wall diameters are consistent. When we’re using cases that exhibit neck wall thickness differences, however slight, having something to final-size the inside of the neck actually produces a more concentric case neck, from the bullet’s point of view (literally). Go with that.

Make life easier on case necks. Many dies have a sizing button that can be chucked into a hand drill (chuck up the decapping stem). It’s way wise to run it against emery paper to polish the fool out of the piece before even its first use. I use 320 grit. The difference in use, and its effect on the case neck, is astounding. If needed, the button can be run on the emery until it’s the right size (smaller) to get the bullet grip we want from the case neck. I’ve encountered a number of .223 Remington dies that needed a smaller diameter button to net the recommended .003″ constriction. And lube the inside of the neck. Right. Some seem adamant about not doing this, but case necks ought not to squeak. I use plain old case lube.

Information in this article was adapted from The Competitive AR15: the Ultimate Technical Guide, published by Zediker Publishing. For more information, including many downloads, check www.zedikerpublishing.com or call (662) 473-6107.
By Glen Zedkier

AR 2


This WW-brand case has .012″-thick neck walls. Double that to get .024″. Add that to the
bullet diameter, .224″, to get the outside case neck diameter of a loaded round. Of course
you can always just measure a loaded neck, but this progression of attaining numbers shows
more. For example, take that figure, .248″, and reduce it until you get the .003″ recommended
constriction amount. That means we need a ready-to-load outside diameter of .245″, which
would be an inside diameter of .221″. If using a neck-bushing die, it would be a .244″, or a
sizing button diameter of .222″, both account for the .001″ spring-back. (Always either add
or subtract .001″ from any sizing appliance to arrive at an anticipated net result. Brass isn’t
completely pliable, or plastic. It will rebound roughly this amount after any sizing operation.)

Winchester-Western
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310 E. Lanark Ave.
Lanark, IL 61046
(815) 493-6360
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2330 Wayne Haven St.
Fort Wayne, IN 46803
(800) 717-8211
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Case Sizing

If you are a handloader, pay attention. Since it’s a semi-auto, full-length spent case resizing for AR-type rifles is mandatory.

There are subtle and often touted differences in most of the better-grade sizing dies, but most standard full-length .223 Remington sizing dies do an entirely adequate job of getting the case to fit back into the chamber, and that’s the focus here. I don’t think it should be necessary to run a small base-sizing die (smaller diameter near the case head) for most competition rifles with the usual chambers, but it won’t ever hurt accuracy.

The main thing is figuring out how to correctly adjust the sizing die body with the press to give the case all the sizing it needs. More is better than less, but too much, as with many things, is excessive.

As a fired case, which is larger diameter and therefore also shorter than it was before firing, gets squeezed to a smaller diameter by a sizing die, it gets longer again. It gets longer until the case shoulder contacts the corresponding portion of the sizing die that is reamed to fit it. Back to the pre-sizing case dimensions: The case body will be bigger and the case will be shorter, but the shoulder area will be located higher than it was prior to firing. The shoulder, therefore, is taller than before. When a case expands fully inside the chamber, its shoulder moves forward as the case head moves back against the bolt, and its body grows in diameter to fit the chamber walls.

Measuring overall case length (base to case mouth) doesn’t really matter, not now at least. What matters is knowing the amount of case shoulder expansion, how far it moved forward or “up.” Of course (of course) there is a tool or two that will show this. Drop-in-style case gages are popular, but the best kind is one that gives a number that corresponds to chamber dimensions.
This next can’t be done without a gage, so get a gage. An option is shown. Use it to measure a new case. Then measure a fired case. Do some math. For best use in a semi-auto, the difference between fired case shoulder height and resized case shoulder height should be .003″. Most cartridge case shoulders are going to be shorter going in when new than they will coming out after being fired. If they’re not, that means the rifle is very tightly headspaced and therefore should never be fired with a round that has a headspace dimension longer than the chamber headspace dimension. It also means your barrel man done a bad thing, unless you requested it.

AR 1

Here is what we’re working with, and for. The case datum line on a .223
Remington is .330″. From the point of that diameter (dotted line) back to
the rifle bolt is headspace in the chamber, so from that line to the base of the
cartridge case is our concern in sizing. Get it .003″ under the chamber height
and we’re good to go.

Gage The Distance

As you’re adjusting the sizing die body downward (threading it into the press) you’re going to use this case headspace gage to check your progress. Again, you’ll see the case getting longer, meaning the shoulder is getting higher, but that’s because the case shoulder has yet to make contact with the die. When it does the case will stop getting longer. Keep threading the die body lower and checking the case shoulder height. When it reaches fired case dimension proceed very carefully but turn the die down a tad amount more. Stop it when the case shoulder is .003″ lower than it was on the fired case. That is called case shoulder “set back.” We have set back the shoulder on this case .003″. Fix the die in place with its lock-ring, and then check more cases at that setting. Call it good to go when it’s showing consistent cartridge headspace gage readings, and (one more time) they are .003″.

It’s easy. It’s also important. I don’t think it really matters to accuracy, but it sho’ does to function. Everyone who has read much about “precision” loading knows there are those who talk about “fitting” a case to a chamber and how that just has to improve its accuracy. Fitting a case into the chamber is more important and that’s why the .003″ set back.

AR 2

This new gage from Forster works extremely well. Their Datum Dial
accommodates virtually all bottleneck rifle cases, as well as having
additional rings that let it be used as a bullet comparator. This gage
measures off the case datum line, which I say is the correct means. Slick.

Bolt Actions

A bolt-action rifle can get away with less, but nothing should ever be run that’s not at the very least .001″ back from fired dimension. I set my bolt-gun cases back .002″ because I want the bolt to close easily. Case-to-case consistency in this dimension might matter to accuracy, but the dimension itself, as long as it’s “enough,” really can’t. If it did then new cases, which can blow shoulders ahead a good deal in some chambers, wouldn’t group as well as they do.

There’s no harm in setting back a case shoulder more than .003″ but the reason for a minimum figure is some improvement in reuse of the future spent cases. There’s less material movement on subsequent shots, and the brass that flows forward does so from the case head. I run that little extra in my AR-15s compared to a bolt rifle to provide a space cushion to the shoulder during chambering. Depending on bolt gap, and whether or not it was addressed by a builder, there’s often a little (to more than a little) additional and unintentional case shoulder set back when a round is chambered. Plus, residue buildup in a chamber can reduce net headspace a might (keep the chamber clean).

I’ve seen sizing dies with problems, and enough times to say, “What’s next?” Generally, the problems are from inadequate capacity to set back the case shoulder. If a die is threaded all the way down to the shellholder and still won’t push back the case shoulder enough to get the fired/sized difference recommended, then the die either has to have its bottom ground down or be replaced by one that will. Threading the die down farther does absolutely nothing but stress the press. The case will only go in so far. Any and all grinding should be done by a machinist, but it won’t cost much and usually is preferable to trying to get satisfaction from the die manufacturer. There are accessory shellholder sets that have different thicknesses but these also won’t solve such a problem. They are handy, though, when loading for different rifles that need different amounts of sizing on their cases.

Information in this article was adapted from The Competitive AR15: The Ultimate Technical Guide, published by Zediker Publishing. For more information, including many downloads, please check www.zedikerpublishing.com or call (662) 473-6107.
By Glen Zediker

Forster Products Inc.
310 E. Lanark Ave.
Lanark, IL 61046
(815) 493-6360
www.gunsmagazine.com/forster

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Columbia, MO 65203
(800) 243-3220
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(800) 717-8211
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Twists And Leads

The Right Barrel

My UPS man flagged me down recently. He told me that (such-and-such) was having a big sale on AR-15 uppers… “Should I get a 9 or a 7…?” He was, of course, referring to the barrel twist rate. My first question back was “What do you want to shoot in it…” I was, of course, referring to ammunition.

The twist rate question is fairly easy to answer, although it has more than one part or qualification. It’s the other question that demands a little more attention. That is, “Is it a .223 or NATO chamber?”

First, twist rate. A barrel twist rate is expressed as the distance for one complete revolution or “turn” of the rifling. It’s a 360-degree spiral. A 1:9″ is read as “1-turn-in-9-inches.” The twist rate must apply enough revs to a bullet to stabilize it. Although it’s really the length of the bullet, not its weight, that determines the necessary twist, it’s usually referenced in bullet weight. The reason I mention this is because there are some bullet designs that create a longer bullet compared to others at the same grain weight. A 70-grain “VLD” (Very Low Drag) design is a good example. These bullets are considerably longer than say, a 69-grain Sierra MatchKing. The 1:9″ will stabilize the Sierra but not always the VLD. VLD bullets are for competitive shooters who handload, pretty much, so will not likely be encountered by others.

So, the twist rate answers: A 1:9″ will stabilize virtually all commercially-loaded bullets up to 70 grains. Anything heavier than that needs the 1:7″ (1:8″ is fine too, just not as common in factory-built uppers). The most common need for a 1:7″ is for those who want to use commercially-loaded ammo with a 75- or 77-grain bullet. A 1:9″ will not stabilize those loadings.

Practical advice? When unsure, go with the faster twist. A 1:7″ twist provides enough flexibility to launch anything up to and including an 82-grain bullet. Accuracy differences with lighter bullets will not be noticeable. By that I mean shooting lighter bullets through a faster twist. The only question might come if someone wants to shoot very light bullets, such as specialty varminting bullets, through a 7″ twist. There can be bullet jacket damage, which can lead to “blown up” bullets if we’re shooting something like a 40 grain at max velocity. Again, this is more likely encountered by the handloader and not the loaded ammo purchaser.
By Glen Zediker

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Buffer Stuff

Keep The AR Cycling Happily

I know the way I write must sound like I think the AR-15 gas system is just corrupt engineering… I’ve spent quite a few words here and elsewhere going on about taming it down so the rifle behaves better.

Overview: An “impulse” gas system is regulated only by tube and hole dimensions. More or less, port pressure (never to be confused with chamber pressure) is the amount of gas pressure at the gas port during firing. Port pressure mostly determines the “timing” of system operation. If too much pressure gets in too soon, the system has no choice but to function. Port hole size and port location down the barrel has much to do with this timing.

Carbine-length systems, in particular, can produce problems. Essentially, if too much gets in too soon, the bolt will unlock too soon as the system begins moving the bolt carrier to the rear. Then, the cartridge case gets yanked while it’s still expanded inside the chamber. This creates the “extraction” problems common to carbines (16″ or shorter barrel). It’s not an extraction problem, really, but a timing issue.

Additionally, an overdose of gas creates overly high-bolt carrier velocity going back against the buffer. It can get so high, and again this is most symptomatic in carbines, that the carrier will “bounce” off its rearward stopping point and rebound overly quickly, going back ahead. Sometimes this appears like a “short stroke” or weak function but its cause is actually just the opposite. Overrides (failure to pick up a round from the magazine) and failures to lock back against the bolt catch or stop can result. The real issue is the carrier is outrunning the other part systems, the magazine specifically.

We are in milliseconds with respect to “fast” and “slow.” Virtually all the influential firearms functions, including breaking a shot, are measured in milliseconds.

So, there is help for all this; altered port locations and sizes (only done on custom re-barreling projects) or regulated gas blocks—or both—make big differences. So, too, do heavier-weight carriers. Those resist initial movement for a speck longer, giving internal pressures longer to subside. The easier means are related to the “back part” of the system, which, let’s say, is the buffering apparatus. It can be altered to influence bolt carrier movement, in both directions. The direction that matters most is going back after firing.

AR2

With any buffer change, make sure there is enough overrun (gap) between
bolt and bolt stop to ensure bolt stop function. A nickle’s width is the minimum.
By the way, a trick that can help bolt stop breakage problems in big-chassis
rifles is intentionally reducing this gap. Easiest done with the little stick-on
buffer pads from Brownells. Only for competition use though! Don’t cut it
closer than suggested, but stock guns usually have an excessive gap.

AR3

If you’re going to tune a spring by cutting coils, count them. Don’t
measure the spring. Rifle “standard” is usually 43, and it’s 37 for
carbines. So, if you want a carbine spring from a rifle spring, count
down six coils and zip it right there. I use a Dremel cutting wheel,
and safety glasses! The side of the wheel can smooth the ends afterward.
Never be afraid to cut coils to get function. Sometimes a lot of mods
to carrier function can require it, but that’s a good thing. Just make
sure the spring is the problem, meaning the cure.

Tools Of The Trade

The buffer itself has a few options on the market. One of the foibles of carbine architecture is the shorter buffer, that’s also a lighter buffer. Increasing buffer weight is effective. Doing this softens carrier movement rearward. The more weight, the harder to push.

Effectively increasing buffer weight, which is a pretty much accurate way to say it, can be done with a different buffer spring. I’ve decided for myself there’s really no such thing as a “standard” spring for rifles or carbines. There are differences in how different examples compress and rebound, and if you measure enough of them you’ll record different lengths. More checks will show, though, that most have the same number of coils. Any more I just trim rifle-length buffer springs to make them work.

David Tubb, umpteen-time NRA High Power Rifle and Long Range Rifle champion, markets a “flat-wire” buffer spring that works very well. It’s made from Chrome Silicon Alloy, a radically better material than music wire. Since the coils are flat, the compressed length or “solid height” of the spring is much shorter than a round-wire spring can attain. That means, if needed, an effectively stronger spring can fit into a carbine buffer tube without hitting solid height and impeding function.

The longer flat-wire spring adds a little extra pressure to aid in keeping the carrier still a tick longer, even though I don’t really see it as an “extra-power” spring. One will increase “in-battery load” about 25 percent. That’s significant.

Another very good product is from ITT (Enidine), The “AR-restor” incorporates a hydraulic component into its buffer. Works like a shock absorber. Works like a charm. Once again, it just slows things down. I’ve been running these in my competition guns for a few years now. It just replaces the standard carbine or rifle buffer (ITT also offers one for “big chassis” rifles like SR-25 or AR-10). Running a rifle with one of these installed is a noticeable difference in feel as well as function.

The only thing I’ve encountered (but only a couple of times) with replacement buffers is making sure there is enough “room” for the bolt stop to function when it all bottoms out. If not, the fix is removing a little material from the back end of the buffer (after determining that it’s not spring length creating the problem), which is easily done since it’s polyurethane.

Any and all of these changes have to be qualified as appropriate for use under one set of conditions. Not all perform the same on different rifles with different ammunition. Make double sure any change in ammunition, especially, is thoroughly tested for function with your setup. Very (seemingly) small changes in pressures, for instance, have big effects, or can.
By Glen Zediker

AR 1

David Tubb’s CS Flatwire Buffer Spring. This spring will last the
life of your AR-15, and your next AR-15….

Brownells
200 S. Front St.
Montezuma, IA 50171
(800) 741-0015
www.gunsmagazine.com/brownells
(Virtually all parts mentioned are
available from this outlet.)

Superior Shooting Systems Inc.
800 N. 2nd St.
Canadian, TX 79014
(806) 323-9488
www.gunsmagazine.com/superior-shooting-systems-inc

ITT Enidine Inc.
7 Centre Dr.
Orchard Park
NY 14127
(716) 662-1900
www.gunsmagazine.com/itt

SHAMELESS SELF PROMOTION
Information in this article was adapted from The Competitive AR15: the ultimate technical guide, published by Zediker Publishing. check www.zediker.com or call (662) 473-6107.

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Pin It

Making Triggers Better.

I’ve said many times the only real way to improve a trigger on an AR-15 is to replace it with something from the aftermarket. There used to be a scant few, now there are a many

Anyone who’s read my books knows those I favor, so this work here isn’t a buyer’s guide. I have found no matter which aftermarket trigger you choose, there are ways to make it perform better, and keep it performing well.

Some come supplied with their own proprietary trigger and hammer pin sets. Pin quality matters. Think about how the system functions, and how much room there is for imperfection considering receiver hole sizes and locations and trigger pieces-parts hole locations, and it’s clear the pins that fit into these holes have a say in how well the truly functional trigger parts (hammer hook and sear) establish a consistent connection, which means a consistent disconnection.

When I can, I push through a set of KNS brand trigger pins. These are true and dimensionally precise. A set of locking-style pins is a nice addition. These usually have an external locking arrangement. If the pins can’t rotate then at the least the trigger and hammer will be rotating on the same spots each cycle. Unless it’s an external lock, then the snugness of the fit with the receiver holes determines whether they stay put.

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Load Development

Crucial to accurate, consistent handloads.

I usually talk here about guns. But, dang, guns are little to no fun at all without ammunition. I thought for this bit it might help some to talk about the process of developing a handload for your AR-15.

New bullet, new propellant, new rifle—anything new means testing and development. For myriad reasons, some known and some I’m not so sure about, one load may perform differently in different rifles, and this new jug of propellant or box of primers may not behave the same as the last batch of the “same” thing.

I do all my load work at the range. That’s another article by itself, but it lets me not only save a whopping lot of time, but also have the opportunity to test combinations under pretty consistent conditions.

There are a number of good loading manuals. Most are done either by bullet or propellant manufacturers, and there’s a lot more data available via magazines. Study enough of it and it becomes plain agreement is unusual. The reason is because of differences in components and equipment, and also testing conditions or circumstances. Published data serves me mostly by establishing an idea of what to anticipate—an important function.

A number of variables apply to a cartridge (propellant, bullet, primer, case), and then an increasingly escalating number of variables introduced through variously combining and fine-tuning all those (bullet seating depth, for example). Reduce variables to a minimum to get accurate feedback from testing. Let’s focus on propellant charge.
Story By: Glen Zediker

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