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Posted: 3/13/2016 1:23:02 PM EDT
A Tale of a 20” Colt A2 Barrel
This Colt 20” A2 barrel started its life on a factory-built Colt 6551. This was a pre-ban rifle, but this barrel did not have one of those evil, havoc-wreaking bayonet lugs; it’s otherwise essentially the same barrel found on the Colt M16A2 and M16A4 as well as “civilian” variants of those rifles. The barrel has a government profile, a chrome-lined NATO chamber and bore and a 1:7” twist. I fired a couple hundred rounds through the barrel while zeroing, chronographing various loads and doing some informal shooting. I did not conduct a formal accuracy evaluation of the barrel at that point in time. After that, I replaced this barrel with a Colt M16A2 barrel with the attending evil bayonet lug to create my M16A2 clone. This barrel sat on my parts shelf collecting dust for a while, until I decided to sell it. I ended up selling it over the Internet. Three months after the buyer received this barrel, he sent me a message demanding a full refund for the barrel claiming that the barrel was junk and that it was never going to shoot accurately. While I was under no obligation whatsoever to give the buyer a refund after having it in his possession for three months, I did so anyway, minus a “restocking fee.” After the barrel was returned to me I decided to conduct a formal accuracy evaluation of the barrel. I installed the barrel on a Colt flat-top upper receiver and free-floated the barrel with a 12” KAC free-float hand-guard. I conducted the accuracy evaluation from a distance of 100 yards from my bench-rest set-up using my hand-loads topped with 55 grain Sierra BlitzKings. This barrel turned in a 3-shot group at 100 yards with an extreme spread of 0.180”. 
This barrel produced a 5-shot group at 100 yards with an extreme spread of 0.516”. 
A 10-shot group fired from this barrel at a distance of 100 yards had an extreme spread of 1.085”. 
Six 10-shot groups fired in a row from this barrel at a distance of 100 yards had an average 10-shot group extreme spread of 1.35”. Not too shabby for a “junk” barrel and actually, as good as anyone could expect from a chrome-lined, NATO chambered government profile barrel. In fact, this was one of the most accurate 20” government profile barrels that I’ve ever tested. ..... |
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Quoted: No. They were just shot at different times, under different wind conditions with different sight adjustments. I mean from Shot 1 to Shot 10, group to group, did this barrel move them vertically in a consistent manner? >Implying there's a stress in the barrel that could be countered with a sight adjustment to be more precise and accurate during a string of fire. |
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I mean from Shot 1 to Shot 10, group to group, did this barrel move them vertically in a consistent manner? >Implying there's a stress in the barrel that could be countered with a sight adjustment to be more precise and accurate during a string of fire. Not really. That's just "how the ball bounced" for that particular group. Over-laying all six of the 10-shot groups that were fired in a row, shows a 60-shot composite group that has the shots fairly well distributed. 
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Quoted: I'll wager the "buyer" was shooting M193 or M855 clone ammo or economy FMJ reloads. It's been my experience that quality ammo shoots great from rack grade rifles. Ball ammo rarely shoots well even from premium barrels. He probably didn't use the coveted Lot#3 that the SEALs use, and didn't discount the fliers.  |
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He probably didn't use the coveted Lot#3 that the SEALs use, and didn't discount the fliers.
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I'll wager the "buyer" was shooting M193 or M855 clone ammo or economy FMJ reloads. It's been my experience that quality ammo shoots great from rack grade rifles. Ball ammo rarely shoots well even from premium barrels. He probably didn't use the coveted Lot#3 that the SEALs use, and didn't discount the fliers.
You have a good memory.
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Great test! Goes to show that even your standard A2 barrel can be plenty accurate if you feed it right and do your part. As a bonus, another test showing that lighter-weight rounds work just fine in a 1:7 twist barrel.
I have to ask one thing though: Any plans to do(redo) something like this with an A1 barrel? I know you did one in the past but I don't know if it used your typical set up and/or if it was irons only. Probably not needed as your previous test was still around 1" regardless of the sight/optic. It would also be interesting to see how a Colt A1 barrel compares to the newer options from Brownell's and Green Mountain. |
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I have to ask one thing though: Any plans to do(redo) something like this with an A1 barrel? Competing With the Past More than thirty years ago, the article “AR-15 Match Loads” by Al Miller was published in Handloader magazine. As you would expect, the article chronicles Al Miller’s endeavors in developing accurate loads for the AR-15. The AR-15 he used in developing his match loads was an A1 version. (Did I mention this was done 30 years ago?) 
Even though the M16A2 replaced the M16A1 as “Standard A” for the U.S. Military in November of 1983, the A1 has several characteristics that many people still find desirable today. Foremost would probably be the light weight of the rifle, which is due in no small part to the A1 barrel. The A1 barrel weighs several ounces less than an A2 government profile barrel (and one pound, 4 ounces less than an HBAR). Comparing the profile of an A1 barrel to an A2 barrel, we see that the weight reduction occurs in the area from the gas block to the muzzle. 
I had an unfired, 20” Colt A1 barrel assembly in excellent condition that I had been saving to use for a 20” KISS type build. As Colt introduced the first AR-15 A2 model to the civilian market around 1984 and stopped producing the A1 Sporter model around 1985, I’m going to take a S.W.A.G. and say that the A1 barrel that I have is over 20 years old! The barrel is stamped “C MP CHROME BORE” and has a 1:12” twist. For his article “AR-15 Match Loads”, Al Miller used six different powders and five different bullets in testing, including Sierra’s 52 grain boat-tail hollow point bullet. He tested his loads off a bench at 100 yards using front and rear bags and a scope. His groups ranged from 0.75” to 2.75”. Unfortunately, he did not fire any 10-shot groups (I guess he didn’t get the memo.:D ) All of his groups consisted of 5 shots each. Using his best tuned load, Al Miller turned in ten, 5-shot groups that had an average extreme spread of 1.075”. While these were only 5-shot groups, I was extremely impressed that he was able to obtain that level of accuracy using an A1 barrel. I was curious to see how my twenty year old A1 barrel would stack-up against his. (Obiously, I had an advantage with the free-float tube.) Using one of my standard handloads for Sierra’s 52 grain MatchKing, I fired ten, 5-shot groups in a row from the bench at 100 yards from my free-floated 20” Colt A1 barrel (using front and rear bags and a scope) with the following results: 0.81” 1.10” 1.04” 1.34” 0.66” 0.73” 1.01” 0.98” 0.93” 1.08” The average extreme spread for my ten, 5-shot groups was 0.968”. Following my standard protocol for accuracy testing, I also obtained three 10-shot groups from 100 yards that measured: 1.39” 1.26” 1.40” Those three, 10-shot groups had an average extreme spread of 1.35” and more importantly the three groups overlayed on each other using RSI Shooting Lab had a mean radius of 0.45”. Here are some pics of the best groups. 
In 1964, during testing for report number DPS-1471, the US Military conducted accuracy testing of production M16 rifles (which had the same barrel as the M16A1.) With the rifles secured in a machine rest, three 10-shot groups were fired (hmm . . . where have I heard that before) from 100 yards using M193 ammunition. The median extreme spread was 3.1”. For nostalgia sake, I fired three, 10-shot groups of IMI M193 off the bench at 100 yards from my A1 barreled upper. The average extreme spread of the three groups was 3.00”. ... |
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That's the set I was referring to. Do you feel doing it with irons vs a scope had any real impact? Assuming it was all locked down the repeatability/precision should be constant regardless, if I am thinking correctly. Nothing is "locked-down" in my testing. I use a front rest and a rear bag. I can shooting more precisely at 100 yards with a high magnification scope than I can with standard A2 iron sights. ... |
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I have to admit, I find my Colt barrels to be more annoying than other barrels I've had. My Colt A2 20" will shoot some match loads very accurately. But it throws POI so terribly between different ammo that I want to spank it. And then I had a LW 16" carbine that I didn't find as accurate as I had hoped. But in the end I think I might have boo boo'd with that one. Because after I sold that barrel I found out that it's possible that my mount wasn't tightened down as well as it could've been. It was a larue mount and I discovered the front attachment was kind of loose and I had to tighten the nut some . However I still think that barrel wasn't that great.
I know it's not the profile though. Because I've gotten some pretty decent groups with my A2 20" with a scope and black hills blue 75 grain ammo. 52's also. And then one time I put my Colt knock off 4x scope on an A1 upper I had for a bit and had a good session. It was an SAK barrel and I was kind of blown away how good it did. It probably would've done much better in Molon's hands..... I do remember trying to give my shots time to cool down in between them. Not a ton, but maybe a bit more than I would with my HBars........ I actually don't remember what kind of ammo that was exactly. But it looks like American Eagle. 55 grain. Which grouped pretty darn good. And I know I shot the 52's that day and they grouped well too. 
I think this was black hills blue 52 grain bthp 
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Yup, looks like a junk barrel to me. Please send it to me for proper disposal. I have a 10 year old that could use a good starter barrel, and there's no sense in giving the boy a good shooting barrel. Otherwise, he might make the old man look bad.  JK. Nice work, as usual sir. |
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I'll wager the "buyer" was shooting M193 or M855 clone ammo or economy FMJ reloads. It's been my experience that quality ammo shoots great from rack grade rifles. Ball ammo rarely shoots well even from premium barrels. The truly hysterical thing about this, is that the buyer claims that he never even fired the barrel. ... |
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Quoted: Mind posting photos of your bench setup sometime? I trust your results, but I've gotta see the setup you are using to be so accurate all the time. I always figured you were on a ransom rest or something.   Biggest equipment difference that most don't use is the BR handguard adapter that resists torquing/rolling which ARs are prone to do because of the round handguard. |
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https://app.box.com/shared/static/8ybmvvks8dyx1t1soslfzpxgah071370.jpg Biggest equipment difference that most don't use is the BR handguard adapter. Quoted:
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Mind posting photos of your bench setup sometime? I trust your results, but I've gotta see the setup you are using to be so accurate all the time. I always figured you were on a ransom rest or something. https://app.box.com/shared/static/8ybmvvks8dyx1t1soslfzpxgah071370.jpg Biggest equipment difference that most don't use is the BR handguard adapter. Neat  I can see how it gets done like that. Molon always has the coolest posts.
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Neat I can see how it gets done like that. Molon always has the coolest posts.
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Mind posting photos of your bench setup sometime? I trust your results, but I've gotta see the setup you are using to be so accurate all the time. I always figured you were on a ransom rest or something. https://app.box.com/shared/static/8ybmvvks8dyx1t1soslfzpxgah071370.jpg Biggest equipment difference that most don't use is the BR handguard adapter. Neat I can see how it gets done like that. Molon always has the coolest posts.
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Mind posting photos of your bench setup sometime? I trust your results, but I've gotta see the setup you are using to be so accurate all the time. I always figured you were on a ransom rest or something. https://app.box.com/shared/static/8ybmvvks8dyx1t1soslfzpxgah071370.jpg Biggest equipment difference that most don't use is the BR handguard adapter. Neat I can see how it gets done like that. Molon always has the coolest posts.
https://app.box.com/shared/static/s6ry2po4pl.jpg ... So it's an arms mount screwed into a block, held between a soft bag and bench vise? That's kind of a genius setup really. I was kind of contemplating something similar with a ball head for a tripod. Just tap a cheapo mount to fit a 3/8" tripod screw on the ball head, then just QD the rifle onto it. Thanks for sharing Molon
Btw, have you accuracy tested the Faxon barrels? I hear they get good stuff, but you are the arf king of accuracy. 
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The truly hysterical thing about this, is that the buyer claims that he never even fired the barrel. ... Quoted:
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I'll wager the "buyer" was shooting M193 or M855 clone ammo or economy FMJ reloads. It's been my experience that quality ammo shoots great from rack grade rifles. Ball ammo rarely shoots well even from premium barrels. The truly hysterical thing about this, is that the buyer claims that he never even fired the barrel. ... WTF? I can't even...what?? That's just crazy. |
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So it's an arms mount screwed into a block, held between a soft bag and bench vise? That's kind of a genius setup really. I was kind of contemplating something similar with a ball head for a tripod. Just tap a cheapo mount to fit a 3/8" tripod screw on the ball head, then just QD the rifle onto it. Thanks for sharing Molon
Btw, have you accuracy tested the Faxon barrels? I hear they get good stuff, but you are the arf king of accuracy.
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Mind posting photos of your bench setup sometime? I trust your results, but I've gotta see the setup you are using to be so accurate all the time. I always figured you were on a ransom rest or something. https://app.box.com/shared/static/8ybmvvks8dyx1t1soslfzpxgah071370.jpg Biggest equipment difference that most don't use is the BR handguard adapter. Neat I can see how it gets done like that. Molon always has the coolest posts.
https://app.box.com/shared/static/s6ry2po4pl.jpg ... So it's an arms mount screwed into a block, held between a soft bag and bench vise? That's kind of a genius setup really. I was kind of contemplating something similar with a ball head for a tripod. Just tap a cheapo mount to fit a 3/8" tripod screw on the ball head, then just QD the rifle onto it. Thanks for sharing Molon
Btw, have you accuracy tested the Faxon barrels? I hear they get good stuff, but you are the arf king of accuracy.
They have graciously offered to send me one of the barrels for testing, but since I don't accept free items for testing from manufacturers, I declined their offer. Once I get caught-up on my test schedule, I may add one of their barrels to The List. ... |
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