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Posted: 3/11/2009 1:02:13 AM EDT
| Have a bushmaster A2 rifle, over 1k rounds through it. Although its probaly 8+ years old. Feeds the first round fine. When I fire it off, the brass is ejected and the second round jams. Every time. Several different mags, several different ammo types. Same problem. I tried putting a different upper on the bushy lower, same problem. I put the bushy upper on a different lower, no problems. So Im quite positive the problem is being caused by the lower. Can it be anything but the buffer spring? |
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How is it "jamming?" Is it a failure to feed, double feed, what exactly is happening to that second round? Did this just start happening?
If it works with a different lower, than I too would guess its a lower problem. If you're using too heavy of a buffer, the bolt may not cycle far enough back to pick up a new round. But that should have been causing problems from the start. Perhaps the hole in the end of the tube is clogged (and air pressure is not letting the carrier cycle properly). Take out the buffer and spring, and give them and the tube a good cleaning, then relube the spring and buffer. I guess those are the first two things that come to mind. |
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A few things to check- sounds to be short stroking. Will it lock open manually? If, not check the length of the upper stock screw. If so, then do the one shot method to confirm bolt hold open.
Could be that the hammer is binding on the bolt carrier causing short stroking. Pull the charging handle back and feel for this with and without an empty magazine. If so,maybe the tail of the hammer is hitting the disconnector. Make sure the pistol grip screw is not too long and touching the underside of the trigger. Pull back the charging handle and make sure the rounds are coming up to the top of the magazine and then ease the handle forward and see if the rounds are being picked up by the bolt. Repeat for several rounds. Make sure the magazines are up high enough in the lower, or not so high that they rub the bottom of the carrier assy. |
| Wont be able to check it out for a few days, but I did switch out the 2 stage trigger that came with it for a standard trigger. Any possibility I could have messed something up. I mean I have put together a few rifles and never had any problems before. Will update after I am able to try it with the new stock assembly |
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Wont be able to check it out for a few days, but I did switch out the 2 stage trigger that came with it for a standard trigger. Any possibility I could have messed something up. I mean I have put together a few rifles and never had any problems before. Will update after I am able to try it with the new stock assembly The hammer could be sitting high and retarding the carrier. Just a guess. Put the old trigger in and see how it runs. |
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would there be any physical evidence of this? I.E. rub marks on top of the hammer or anything? Trigger/hammer is RRA just like the original. Dont have the other trigger to put in it anymore 
Ill see what I can come up with Tail of the hammer hitting the disconnector will cause a small notch or dent on the top of the disconnector and a corresponding spot on the tail of the hammer. |
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would there be any physical evidence of this? I.E. rub marks on top of the hammer or anything? Trigger/hammer is RRA just like the original. Dont have the other trigger to put in it anymore
Ill see what I can come up with Tail of the hammer hitting the disconnector will cause a small notch or dent on the top of the disconnector and a corresponding spot on the tail of the hammer. Not to hijack, but I have a similar issue with the same type of malfunction, and it looks like the hammer tail is contacting the disconnector. It's a frankin-gun - LWRC 16" upper/RRA lower w/ standard 1 stage. How would you remedy the contact between the two parts? |
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would there be any physical evidence of this? I.E. rub marks on top of the hammer or anything? Trigger/hammer is RRA just like the original. Dont have the other trigger to put in it anymore
Ill see what I can come up with Tail of the hammer hitting the disconnector will cause a small notch or dent on the top of the disconnector and a corresponding spot on the tail of the hammer. Not to hijack, but I have a similar issue with the same type of malfunction, and it looks like the hammer tail is contacting the disconnector. It's a frankin-gun - LWRC 16" upper/RRA lower w/ standard 1 stage. How would you remedy the contact between the two parts? You can bob the tail on the hammer.Look at a two-stage hammer,works fine,just very hard steel to cut. |
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