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Posted: 7/28/2003 3:56:40 AM EDT
Well it figures. I just received my approved form 1 in the mail last Saturday, so I headed to the range this Saturday to shoot my new SBR for only the second time. I have actually had this lower for several years and probably have a couple thousand rounds through it. I only got through about 90 rounds this Saturday before I had my first ever malfunction. After ejecting an empty magazine and inserting a loaded one, I attempted to release the bolt with the bolt release button but noticed it had no tension. I then tried to release it using the charging handle, but this did not work either. Basically the bolt was jammed in the open position. After scratching my head for a few minutes, I decided to pack it in as I had no screwdrivers to remove the offset pin to separate the upper form the lower. I went to my favorite gunsmith since he was closer than home, and we managed to get the two halves apart. When we did, a small piece of metal fell out of the lower. A brief inspection reveled that the bolt catch had actually sheered off and became wedged under the bolt, preventing it from closing. My smith said that this wasn’t all that uncommon, but in eight years of shooting AR’s I have never before seen this happen. In the end the gun will now function again, and no permanent damage was done, but is this a common failure item? Should I have a couple extras on hand? Was there anything I could have done to prevent this from happening, like using the charging handle vs. the release button to close the bolt? Any input or experience anyone has with this would be greatly appreciated.

-Matthew
Link Posted: 7/28/2003 11:17:54 AM EDT
The 9mm bolt catches do break, in fact the 9mm catch is stronger than the 223 catch. So if you order a few new ones, make sure that the new ones are the colt 9MM ones.
Link Posted: 7/28/2003 2:10:00 PM EDT
I've gone through several bolt catches on my 6450, and haven't found out why they break. I use only old stock colt replacement catches. If anyone has any ideas or fixes, please speak up!
Link Posted: 7/28/2003 2:16:18 PM EDT
To resolve the problem with the catches, you need to limit the amount of room that the bolt can go past the catch (added spacer behind the existing spacer, electric J box knock out plugs will work), and slow the bolt down (use a heavier buffer, a strong spring just increased the forward stroke speed). The reason that it snaps is the bolt goes too far behind the catch (more than a 1/8" gap), and with hot ammo, the buffer bounces off the back of the receiver extension, and crashes into the catch.
Link Posted: 8/2/2003 5:39:07 AM EDT
(added spacer behind the existing spacer, electric J box knock out plugs will work), Can you elaborate (explain) this to me in idiot's terms? I can't picture what you are describing. Thanks again
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