Originally Posted by
Danny
A few years ago, I used my AR at the National Matches. I popped some primers. I put the rifle away for a couple of years. When I went to use it again, I found that the bolt would not lock back on the last round. I cleaned the rifle thoroughly, especially in the areas around the trigger, the bolt lock and the buffer/buffer tube. I think that I probably changed out a bolt lock set, as well as stoning the back surface of the bolt lock to make sure it was operating freely. I cleaned out the magazine, changed the spring, and might have even tried another magazine. I put a new buffer spring in. Nothing changed anything. It was asked if I thought that my front sight and gas port were not lining up. That was somewhat of a thought, but knowing Frank's machining, I considered it highly unlikely. I can only assume that the issue is that I am somehow losing gas (least likely), or impeding bolt travel. I have come to the conclusion that I may be impeding/retarding bolt/buffer movement by greasing the buffer and buffer tube. Now, I have always done this in my Bushmaster, but that does not mean that it is proper or will always work. Someone also mentioned the vent hole in the upper buttplate screw. Neither of mine have that, but one lower works flawlessly. Through research, I have come to conclude (most likely) that this is a drain hole for battle conditions and not to relieve pressure between the back of the buffer and the closed end of the buffer tube. From memory, it seems that the clearance between the buffer and tube is enough to equalize pressure on both sides, and anyway, your shoulder covers the vent hole during firing. I am wondering if my greasing might, with no screw vent present, be overcoming the built in clearances, causing just enough pressure build up behind the buffer to impede some rearward velocity. I noticed something odd with my buffer that I will touch on in another post.
Once, in the past, with my Bushmaster, I was able to get the rifle to malfunction by greasing the bolt/receiver area like a Garand. I stopped doing that there, and my problems went away, though I continued with greasing the buffer/buffer tube. That is another reason why I think that greasing the buffer/buffer tube in this rifle might be part of or all of the trouble.
Danny