Posted: 3/7/2007 8:54:09 AM EDT
I wanted to post a few pictures of the problem with the buffertube that I described in the LE Commando post above. The lower on the left came fromt he factory in the condition that I described, where the tube needed to be treaded in one more turn to properly seat up against the buffer retaining pin, I removed the buffer tube and installed it like it is suppose to be. The middle lower is one that shows the way it came from the factory and if run like this it will eventually cause a stopage and exhibit the cracking that you see on the bushmaster lower on the right. I learned this some years ago the hard way. Check your new Colt rifles, all models to make sure that your buffer tubes are positioned right so that you don't end up with a cracked lower. The middle one I actually had to take a file to the lower inside of the buffer tube to get it to thread up and sit on the buffer retaining pin like it is suppose to. Hope this helps some of you guys.  
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| I had to unscrew the buffer nut, which is a pain because they are staked, then turn the tub in 1 more complete turn so that the edge of the tube rested against the pin the way it is suppose to. On the first one, it was fine, just screwed the tube in one turn, and resecured the buffer nut. On the second one, I was about 1/8th of a turn away from making a complete revolution and the buffer tube had already bottomed out of the retaining pin. If I unscrewed it, it was like the one pictured in the middle. If I tightened it all the way around, it pushed against the pin too much and did not allow it to float up and down, which it needs to so that you can get your buffer out. So I completely removed the buffer tube and filed just a few thousandths off the lower side of the buffer tube so that when screwed into the receiver where it needs to be, the buffer pin isn't completely in a bind. My dad also bought a 6933, all 2 of ours are consecutive serial numbered, and his was fine. I just wanted to post it so that no one ended up with a lower like what happened to that bushmaster. I had bought the bushmaster used a few years ago and didn't know to check it, and one day at the range, she quit. Totally bend the retaining pin up and cracked the alumnuim around the pin. |
| Given that the buffer isn't supposed to come in contact with the retainer pin during firing I don't know that the issue is with the tube. The tube simply holds the pin in place so it doesn't pop up into the receiver. The real issue is that the buffer is smashing into the pin on the Bushy which indicates other problems. |
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I am not so sure that a barely covered buffer retainer pin is a problem. I have had at least one AR, a Bushmaster, with a buffer tube that barely covered the buffer retainer pin, as pictured, with no issues after a couple of thousand rounds. I agree with Bradd_D that when the buffer hits the retainer pin, thanks to a misaligned bolt carrier not holding the buffer far enough back, that is a problem. I remember complaints about this very issue with Bushmaster a few years ago, raised by Pat Rodgers IIRC. The face of the buffer gets a circular ring around the edge where it smacks into the pin. My 6933 does have the tube only slightly cover the buffer retainer pin. What was the round count on the Bushmaster when the metal cracked? Did the Bushmaster buffer have a circular ring around the edge? Nonethless, thanks for raising this concern, the pictures, and I will keep an eye on my 6933. |
| I took about 8 to 10 rounds with the Bushmaster that I had before it broke. I had inspected the rifle well when I bought it and it did not have the cracked area that showed up after it quit firing. When it quit, it guit. I have since made it a habit to pop open all my AR's to look for this. I even noticed that LMT's buffer tube that comes with the SOPMOD stock has a half U shaped cradle that makes a semi circle around the buffer retaining pin, which further helps hold it in place. An A2 stock can only thread on so far due to the lip at the end of the threads and when you tighten it down, it sits right against the buffer pin just as the lower on the right and left do. I really liked how the LMT buffer tube straddles the pin, just looks more secure. The problem with the tube barely sitting up on there is that it allows for just a little extra play when the buffer hits it, and over time it will wear out that this piece of alumnuim that holds it in. I got to looking at the buffer on the Bushy and it did have that wear pattern that you described. I only posted cause I have had a problem with it before and wanted to give everyone else a heads up. |
The only time the buffer should come in contact with the pin is when you break open the action. The pin's sole purpose is to retain the buffer when the receivers are seperated. If contact is made any other time, something is out of spec. When you close the action look to see if the buffer is pushed back a bit by the rear of the bolt carrier. If not, there is your problem. The amount of contact between the buffer tube and retainer pin is irrelevant. |
My 6933 has 540 rounds so far, no problems. The buffer shows no unusual wear and when I close the action the bolt carrier pushes the buffer back so it does not touch the pin. I_hate_taking off a staked castle nut : (I did it once to unban an MT6400). So I will just keep a watchful eye on mine. Hopefully I will have some new PMags soon to run some more rounds through it :) |