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.) 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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Originally Posted by dewatters
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