I recently aquired a used Colt 6721. It came with an unshrouded firing pin type half moon carrier, blue extractor insert, carbine buffer and gas rings which allowed the bolt to collapse on itself. Since its a used gun and ammo is pretty much unobtainable I decided to try to do some maintenance before I took it to the range. I put in a new BCM buffer spring and H-Buffer, new BCM gas rings and a new BCM extractor sping, black insert and O-ring.
I finally obtained some ammo and a few magazines so I tried to chamber a few rounds just to see how things were going and got some bad news.
[IMG][/IMG]
[IMG][/IMG]
This happened only when hand cycling the action, never from a locked back bolt. It happened on one horrendous GI 30 round, one new old stock British 30 round and one brand new Colt 20 round. Occasionally it would completely fail for pick up a round from the magazine but I believe that may have only been from the old GI 30 round (I could be mistaken).
I was careful to make sure I was pulling the charging handle all the way back and not riding it forward and it locked back on all the empty magazines so it does appear to be clearing the bolt catch and ammo in the magazine. Also, after changing the gas rings, if I rode the charging handle on the gun while empty the bolt would not fully go into battery but would once I pushed the charging handle the rest of the way forward.
I tried removing the o-ring and nothing. I tried changing the gas rings back and it resolved the issue when riding the charging handle but I still experience the above malfunctions. I also switched back to the old buffer/spring and it seemed to experience less malfunctions, but they still occurred. The only thing I have not tried is going back to the old extractor spring/insert because I can't really see how that could be the problem, but who knows.
In addition to changing those parts I also tried removing the firing pin because I read that the unshrouded firing pin can catch on the notch of the hammer and someone on TOS suggested that as a quick way to check, it is not. (For anyone who has not tried to work their action with no firing pin, DO NOT EVER DO THIS. I had to remove the receiver extension to seperate the receivers and get the bolt out.) I then tried the proper test and removed the hammer, this also did not solve the problem. Finally, I tried tightening the magazine catch one turn which also had no effect.
So now I am at a loss. Any ideas? (Also the top image insists on being upside down for some reason, because that just seems to be my luck.)


[/IMG]
[/IMG]
Reply With Quote
[/IMG]
[/IMG]


Bookmarks