Building A Wildcat .20

From Brass To Gun.

By Vince Sullivan
Photos Mike Cocita

Published In The GUNS Magazine 2012 Special Edition.

On my first prairie dog hunt, the boys and I were shooting every .22-caliber centerfire rifle we owned: from a .218 Bee to .22-250 Remington and everything in between. Then one of the old boys broke out his secret weapon, the “.20 Varmint/Target” (VarTarg). We watched in awe as this little single-shot rifle began dispatching prairie dogs out to 300-plus yards with no problem. Creating a nice starburst action as the dogs vaporized right before our eyes. This is how I was introduced to the .20 VarTarg, and after coming home from that hunt, I had to have a .20-caliber rifle, which would be my first wildcat cartridge.

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Nothing but the best components for this project


Before the first .20-caliber, factory cartridge (.204 Ruger) came about, “twenties” were not known by most shooters. Only some dedicated varminters and wildcatters played around with .20-caliber variants. However, in recent years .20-caliber cartridges have become very popular. Today’s small-caliber shooter finds a wide selection of barrels, bullets, reloading dies and accessories. The five most popular .20-caliber cartridges seem to be the .204 Ruger, .20 Tactical, .20 PPC, .20 BR and .20 VarTarg. Probably the most efficient of the bunch is the .20 VarTarg. The average powder charge is only 20 grains, while the other cartridges average between 25.5 to 30.5 grains, depending on the powder you use.

Thanks to the Internet, I was able to do my research to find out how much work it would be to make brass for this little rocket and soon came to the conclusion .221 Remington fireball brass was not readily available. Also the forming dies were expensive and fire forming was more work than I was prepared to do. Looking at other options, I found an article on the “.20 Practical”; the easiest, most cost-effective way to get in the .20-caliber game, without going to a factory-loaded cartridge like the .204 Ruger. Simply put, it’s a .223 Remington case necked down to .20-caliber. Already having a rifle in .223 Remington and a set of full-length sizing dies, all I really needed was one of Redding’s Type-S neck-sizing die in .223 Remington, two or three different diameter neck-sizing bushings and a smaller decapping rod assembly with a .204-diameter sizing button and I was in business.

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Next came the issue of not wanting to change the barrel on my .223 Rem. I had to find a project rifle with the right bolt-face diameter and action length, and soon came across a rifle chambered in .17 Remington, which would work just fine for my intended purpose. With no real experience in re-barreling a rifle, I was back on the Internet looking at rifle barrel manufacturing companies and the services they offered. They all made .20-caliber barrels, with a variety of different twist rates. But Pac-Nor Barrels was the only manufacturer who offered .20 Practical in the wildcat listings on their website. After talking to other people I know who have Pac-Nor barrels and are very happy with the performance, I shipped off my barreled action to have a new .20-caliber barrel contour matched to the old one. Once returned there would be no more work needed for the rifle, except to put the action back in the stock and do the barrel break-in to Pac-Nor’s recommendations.

After receiving all my supplies needed for the project I began brass work. Taking small samples of brass from different manufacturers, you first need a full-length size .223 Rem. die before you start the necking-down process. The OD (outside diameter) of the .223 Rem. neck after sizing is roughly .246″. I necked the brass down in increments, starting with a .235″ diameter bushing first and then going to a .230″ bushing. Depending on the brass manufacturer’s neck thickness you may have to go down to .228″ bushing or smaller to get the right bullet tension you require — .001″ bullet tension seems to work best for me. In my necking down process, a .204 diameter-sizing button was not used because I was using a Wilson case trimmer with the appropriate case holder. I trimmed the case length and inside neck ream of the cartridge to .203 diameter. This would give me 5/10″ diameter difference per side or .001″ bullet tension. (Depending on your brass, your final bushing size may be different.)

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After you find the size you like, the brass will have a slight doughnut at the base of the neck. Seat a bullet in a case with no powder or primer and chamber it in your rifle. Depending on chamber clearance, if the case is a little tight it is best to neck ream or turn the outside of the case up to the shoulder, whichever is easier for you. This will help avoid a possible pressure problem. If after you chamber the cartridge the bolt closes with no interference, it should be ok to shoot as is.

After trying all the different brass and getting good results with all, my preference was the Lapua brass because after sizing to .230″, neck reaming the ID (inside diameter) to .203″ and turning the OD enough to even neck thickness by removing just the high spots. The loaded case gives me an OD of .231″. The chamber of the .20 Practical is .233″ in the neck area, which is only .001″ clearance all around. Tight for most, but if you keep your chamber clean it shouldn’t be a problem. After firing I only have to size down my brass .003″, which should result in long brass life.

One of the best-kept secrets to accurate reloading is bullet-seating depth. By precisely regulating the bullet depth and the resulting “jump” (free-travel or clearance between bullet ogive and the barrel lands) can make the difference between OK accuracy, and real tack-driver performance.

Hornady’s Lock-N-Load Precision gauges and modified cases are the easiest tools to use for this task. Starting with a modified case, Hornady makes several series of cases in most of the popular cartridges. If you are shooting a wildcat cartridge you can contact them directly; they will be happy to make you a modified case for your rifle. All you have to do is send two fired cartridge cases for them to look at, along with a check for the dollar amount required. One of the two will be used for your modified case and both are returned to you. This service for me was very prompt and much faster than I expected. Needless to say, I am very happy with the results.

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Having the correct tools is critical when building precision rifles and ammo.

Overall Length

To determine the overall length you need an O.A.L. gauge that threads into your modified case and insert a bullet into the case mouth. With the bolt removed, slide the gauge-assembly forward, snug into the chamber. Gently slide the bullet push rod (plunger) forward until the bullet makes contact with the lands. With a little practice, you can feel the bullet make contact against the origin of the rifling. Tighten the thumbscrew on the O.A.L. gauge; this will lock the push rod and bullet in place. Now you can remove the assembly from the gun. The gauge has a measuring slot located directly at the base of your modified case. With a pair of calipers, you can now measure the cartridge’s overall length. To be more precise, a bullet comparator with caliber-specific insert is more accurate because it will register on the bullet ogive — the part of the bullet that makes contact with the rifling first. This overall length operation should be performed with every bullet type and manufacturer you intend to shoot in your rifle; even if they are the same weight because, for example, Hornady’s bullet will be different than Sierra’s as to where the ogive on the bullet is located in its overall length. Overlooking this can result in a pressure difference as it relates to seating depth in your rifle. (Throat is the area from the end of your cartridge case to where the rifling begins.)

Most barrel manufacturing companies can give you some good advice. When it comes to bullet jump they generally have a lot of knowledge on this subject, and get good feedback from customers, who are happy to share their success with them. The most common barrel length for varminters is 24″. But after doing some research on optimum barrel length, the average velocity increase from a 24″ to a 26″ barrel was about 150 to 200 fps. I decided to go with a 26″ barrel, hoping to obtain the velocity I was after with a reduced powder charge. If things didn’t go as planned the barrel could always be shortened.

A good starting point for loading the .20 Practical would be to use .204 Ruger information starting on the low end, minus about 2.5 grains of powder, and working up from there. Most powder manufacturing companies have web pages with loading information to help you with a good starting point in your load development. Like most reloaders, I generally start with powder already on hand; here is a list of powders used at the time this article was written. DuPont IMR 4895, IMR 8208 XBR, Ramshot X-Terminator, Hodgdon’s Varget and BL-C(2). All the powders produced 5-shot groups smaller than a nickel at 100 yards, ranging in velocity from 3,500 to just under 4,000 fps with 32-gr. bullets, while keeping the powder charge between 25 to 25.5 grains. The best accuracy for me was attained using DuPont’s IMR 4895, IMR 8208 XBR and Hodgdon’s Varget, all at 25 grains. This kept the velocity under 3,700 fps and group sizes well under a dime at 100 yards with no sign of copper fouling in the bore.

WARNING: For your own safety, ALWAYS reduce all starting charges by 10 percent and work up carefully! Ambient temperature changes, powder lot variations and differences in barrel friction can result in significantly increased pressure.

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L to R: .218 Bee, 20 Practical, 22-250 Remington


The goal for me when building this varmint rifle was accuracy, reducing barrel heat and copper fouling of the bore while maintaining good bullet speed. With the .20 Practical you can easily reach velocity of over 4,000 fps. But I’m not sure you will shoot very long before copper fouling the bore. For that reason, I wanted to keep the bullet velocity under 3,800 fps. Hopefully with reduced velocity and powder charge this rifle will shoot all day long without losing accuracy.

Now, when the boys and I are relaxing after a day afield they can talk about how they need a .20 Practical.

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One thought on “Building A Wildcat .20

  1. Mark rosenbaum

    Great article I only recently bought a .223 and now I think it will become a .20 practical


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