I have well over a decade’s worth of experience with the AR-15 rifle and have had the benefit of being instructed in its use in military, police, and civilian arenas. As a result, I have developed a certain amount of proficiency with this weapons system over the years. Learning to clear malfunctions is an integral part of this training and I have had the opportunity to deal with most of the possible malfs this type of firearm can spring on you. I have also soaked up most of the armorer skills necessary to accomplish about any modification or maintenance that the rifle may need.
All that being said, I had a malfunction recently during a range training trip that left me stumped. About six shots into a string of fire my BCM carbine abruptly went single shot only. The rifle would perform all the necessary cycle of functions except I had to manually operate the bolt via the charging handle to feed the rifle the next round. I had recently attempted to clean the lead out of my barrel after mandatory department training with .22LR conversion kits (don’t get me started) because the lead fouling in my 1:7 twist barrel had greatly eroded accuracy.
I am unfamiliar with lead and this type of heavy fouling and my initial thought was that because I had cleaned the barrel the night before with an aggressive compound I had somehow blocked the gas port or obstructed the gas tube. I took the rifle apart and checked the relevant areas for an obstruction and to make sure the gas key was still tight, which it was. At this point I had no choice but to take the rifle home for a detailed strip down and continue hunting for the problem.
I ended up beating out the tapered front sight pins and removing the front sight base (FSB) from the barrel and removing and cleaning the gas tube. After checking the gas path from the port in the barrel all the way back to the gas key I did not observe any signs of an obstruction. All I got for my considerable amount of wasted effort was a marred finish after removing the FSB from my nicely duracoated barrel. I took the rifle out again the next day with some other experienced shooters. The rifle still continued to function only in single shot mode, which was quite frustrating.
I tried using a different bolt/carrier and the rifle worked flawlessly, so we at least had the problem isolated to this parts group. I subscribe more or less to the Pat Rogers school of thought when it comes to cleaning – keep the gun well lubed with quality lube and don’t waste a lot of time doing unnecessary cleaning. This is quite a (welcome) departure from my USMC days, although I did receive some well earned wise cracks about the carbon build up inside the bolt carrier. However, I refused to believe that some carbon buildup would render the rifle suddenly single shot.
Finally, Matt noticed that there was an obstruction deep inside the gas key after a pipe cleaner failed to go all the way through. I had checked the tightness of this thoroughly, but I had neglected to detect the obstruction when I just visually inspected the gas key. The obstruction was a primer that had apparently blown out of a spent shell casing at the exact right instant in time to be hammered into the hole at the end of the gas key and literally peened in place by the end of the gas tube.
I then drilled a small hole in the stuck primer and then inserted an appropriately sized wood screw and gave it a little twist. That allowed the aggressive threads to lodge the primer over the end of the screw and I easily removed the whole mess with the aid of a bench vise and a sharp tug. After a couple of cleansing passes with a pipe cleaner to get rid of the metal shavings, I applied an aggressive dose of fresh lube, and that somewhat dirty (on the inside) rifle was back in the fight!
The above incident was a great reminder that every trip to the range is an opportunity to continue the never ending cycle of learning. Also, no substitute exists for thoroughness and if I had exercised a little more of that initially I would have saved some time, not to mention the finish on my barrel. I hope this example will be helpful if you ever find yourself facing a similar malfunction with this type of rifle.