In a filthy firearm.
As a young Marine captain, I was the new officer on a rifle team and remember asking the grizzled old salts who had shot in many an inter-service championship or Camp Perry what the proper cleaning interval was for those incredible Quantico-built National Match M16s. The answers varied from daily on one end to at the end of the season on the other. There didn’t seem to be any real testing to support any given answer, and I accepted that you punched the bore whenever it seemed right.
I recently thought back on that experience as I finished up an endurance test on a Bravo Company Manufacturing (BCM) upper receiver. Over the course of a little more than three years, I had logged the lubrication intervals using FireClean to see how far the AR would run as it got dirtier and dirtier. At the end of the test, I was in possession of a barrel through which I had logged 10,000 rounds and had never cleaned in any manner. In shooting the last thousand rounds or so, I had noticed that the rifle seemed to be still shooting quite well and thought it would be interesting to do a formal accuracy workup. I borrowed a Bushnell Elite 4.5-18×44 LRTS riflescope to give the barrel every chance to succeed, and grabbed some quality ammo.
All firing was done from the prone position with the rifle supported by a Harris bipod in the front and some bags under the toe of the stock. The rifle had a Geissele Super V trigger, which is an excellent duty and snap-shooting unit, but not normally associated with group shooting. The BCM wore a free-floated KeyMod aluminum KMR-A rail and the barrel was a basic government profile 16” with a mid-length gas system and a 1:7” twist.
I fired a couple of sighters to get the LRTS on paper and then the very first five-round group of Hornady Steel Match clustered five .224-cal. holes into a tight .84” group that could be covered by a nickel. That was pretty close to prophetic, as the average of all five groups with the Steel Match ran .89 from the filthy barrel, with the series tallying .84, .85, .86, .72, and one lonely group over one minute of angle at 1.17.
That performance wasn’t an outlier. After 10,000 rounds, the BCM barrel grouped Federal Varmint hollow points into just barely over 3/4 m.o.a. on the low end and averaged just over an inch due to one “large” 1.5” group that pulled the average over one MOA.
Black Hills 69-gr. Sierra Match Kings clustered together consistently, poking holes in a tight knot while maintaining polite separation for each hole at just under a minute on average with .79, .82, .90, .92, and 1.25” groups.
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I was somewhere between pleasantly surprised and mildly shocked for the barrel to do this after 10,000 rounds and never had as much as a boresnake, brush, or patch run through it.
I’m not surprised. Eugene Stoner engineered a fine system. Of course, I wouldn’t recommend doing that – this was a stress test of sorts. Increased fouling and friction will only increase wear and metal fatigue. But it’s nice to know that the delivered wisdom may not be so wise after all.
It’s funny how old myths die hard. My son never had any complaints with the weapon system so I never came into it with predisposed prejudice.