Accurate Bullet Delivery
Is “All About The Tube”
By Glen Zediker
This is probably about the 20th time I’ve written such an article, but it is important. Basic understanding of elemental components aren’t inherent, and there are always “new” folks out there needing to know. So this time I want to talk about the most important component to accuracy in any AR-15. That there would be the barrel.
I freely admit to being a barrel snob. I’m a competitive shooter and I want all the points I hold for. The only way to ensure peak accuracy is to install a truly good “match-grade” barrel.
Now, you can’t swing a dead cat without hitting somebody’s “match-grade” barrel out there in our industry. Folks, no objective standards apply. None. “Match-grade” is a term entirely freely applied. To me, a true match-grade barrel will win championships. There are more, but here are three names to know: Krieger, Lilja, Schneider. Satern fits in there too.
The best way to judge the quality of a barrel is by cost. Sorry. But it’s true. A handmade or custom-made barrel is expensive. It costs a lot to produce because of the quality controls. It takes time.
For the do-it-hisselfer, Satern Custom makes a truly good barrel available
ready to torque down onto your upper, correctly headspaced (bolt included).
Glen anticipates barrel replacements by following a “motor racing” philosophy where
all parts have a stated service life. They get replaced on schedule, regardless of
“perceived fitness.” It’s how to keep a race car—and a race-gun—winning. Glen uses a
Hornady Chamber All Gauge to monitor throat erosion. When it hits 0.150, he knows
the barrel is done.
There are tiers of “good” barrels. Those from the first tier, represented by the makers I named. The next tier are “graded” barrels: these are produced relatively en-masse and then checked over for things like straightness and end-to-end uniformity. Shilen, Douglas, and Pac-Nor offer such options. The other tier are barrels that are maybe good, maybe not. They can all claim to be “match” barrels. This last follows the PDL grading method: Pure Dumb Luck gets you a tube that hammers. Some of my Colt HBAR barrels shot as well as all, and others didn’t.
I no longer tell everyone they need to have a truly good barrel. Truly good barrels are ballpark $500, ready to shoot (turned to contour, extension fitted, chambered, port drilled, assembled onto the upper). A little less maybe, but not much. What do you get with a truly good barrel? I’ve had enough experience with this to tell you such a barrel, correctly chambered and installed underneath a likewise correctly done free-floating fore-end tube, will easily group under 1 MOA, often well under. Not can, will. If your AR-15—no matter the barrel dimensions or length—won’t shoot under an inch at 100 yards, then there’s your solution. And now consider your judgment: what level of accuracy do you expect? If you can be happy with groups between 1 and maybe 1-1/2 MOA, then something from the “second tier” will be rewarding. Anything lower than that could be, well, anything…
Another thing a truly good barrel has had done is stress-relieving. This process varies from maker to maker in specifics, but the point to it is to eliminate any heat-induced warpage issues. Some barrels, especially small-diameter profiles, can “look” to a different point when they get hot. This factor is extremely important in a carbine-style barrel. If you want a light barrel that shoots well, it had best have been properly stress-relieved. Internal finish also favors the custom barrel. They’re all hand-lapped.
Stainless or chromemoly? Stainless. Stainless doesn’t shoot one bit better, but it shoots at its peak accuracy longer. Usually to the tune of about 15 or 20 percent more “best” accuracy rounds. The problem with stainless is when it stops shooting its best, it stops right then and there. It’s abrupt. Chromemoly tends to fall off over a narrower cone of shot dispersions and will still shoot “OK” for a good number of rounds after it’s lost its edge.
The two materials wear differently and this is a culprit in the discrepancy. First, barrel “wear” is virtually all in the chamber throat (it’s the area immediately ahead of the cartridge case neck area within the chamber). Focused burning gases eat away at the barrel steel, deteriorating it. The commonly used term is “throat erosion,” and that’s descriptive.
Stainless vs. chromemoly is another endless argument. Stainless steel will give
more on-point accurate rounds, but when they quit, they hit the wall. Chromemoly
has a less notable decline, meaning less noticeable. They’ll shoot “pretty well”
for a pretty long while. If you want to shoot the heck out of a barrel, go with
chromemoly. Of course, corrosion resistance favors the stainless.
Looking at the throat area of seasoned stainless and chromemoly under magnification, they’re quite different. The stainless surface looks like a dry lake bed. It will have cracks between flat areas. Chromemoly will have an overall roughened appearance, like coarse sandpaper. I think this is why the stainless shoots better longer: the bullet can still ride the smooth flats OK for a spell. Well, until the cracks get too big, then it’s like a cheese grater. It just rips at the bullet jacket. The chromemoly more or less just continues to rough-up the jacket, to abrade it but not necessarily as severely as the very worn stainless throat will.
As counterproductive as this may sound, testing by myself and others seemed to show we continue to get better groups for a little longer time if we abandon the use of a copper-solvent in stainless barrels. Seems the fouling hiding in the cracks makes a smoother surface. I noticed this after seeing the more age the barrel got, the more and more rounds it took to settle back in on zero after a thorough bore cleaning. I’m not saying don’t clean your barrel: just don’t use anything with ammonia in its later stages. And, speaking of such, how long does a barrel last?
An AR-15 barrel lasts around 5 seconds. Put another way, say, 5,000 rounds at one millisecond per round (which is the approximate amount of time the bullet spends inside). How many rounds is partly subjective. A High Master is going to think a barrel is done before a beginner will. And there are some very good shooters who report upwards of 7,000 accurate rounds.
The primary contributor to the progress of the severity of throat erosion is bullet weight. Even though a smaller, lighter projectile has more burning propellant behind it, it’s the slower acceleration of the bigger bullet that does more damage. The intensity of the flame-cutting is higher over a shorter distance. So a steady diet of 50-grain bullets extends barrel life over constant use of 75’s.
Next time, more and more specifics. I want you all to understand barrels! It’s the most important part of your rifle.
The preceding was a specially adapted excerpt from The Competitive AR15: The Ultimate Technical Guide, by Glen Zediker and Zediker Publishing. Check it and other materials by Glen at ZedikerPublishing.com or BuyZedikerBooks.com.
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