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Posted: 10/8/2010 1:00:01 PM EDT
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Buddies new DPMS in 7.62x39, bolt does not lock back sometimes. He's shooting steel case Russian ammo fed from C-Products mags. AR probably has just over 100 rounds and mags brand new. I think it's short stroking because a couple of times, bolt cycled and failed to pick up a round. I recommended that he shoot a couple hundred rounds to loosen things up and wear in the spring before he looks for lighter springs or buffers. The bolt locks back fine by hand and misses locking back one in six times.
Any thoughts? |
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Break in time needed,
Lack of CLP lube and correctly cleaning (the chamber not being chamber brush scrubbed). Have him get the round count upwards of 500 rounds (with cleanings), then get back to us once the rifle has broken in (parts have self mated) if he still has problems. Also, point him to the cleaning forum so confirm that he is cleaning and lubing the rifle correctly, including the correct solvents to use as well. If at that time he is still having problem, then we can start looking at spring and gas port tweaks for the ammo at hand (read chances are the rifle will run fine with brass case ammo now). |
| That's what I told him too. He reloads but bought the 7.62 because the steel case ammo is cheaper than reloading but had some problems with light primer strikes from day one... I posted his problem here and the firing pin protrusion and the solution worked. I told him that he should take advantage of the "cheap" ammo and send more rounds down range...but he did not take the advise to heart. Oh well... Thanks! |
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Best bet not an ammo problem per say, just the chamber may be a tad tight for such to release cleanly once fire formed.
With life fire and cleaning, it should both polish the chamber and slightly enlarge it so the ammo no longer has a problem on extraction (think BM and wolf ammo). |
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Update to my buddies problem...
I had recommended that he shoot at least a few hundred rounds to break-in his DPMS but he is convinced that there is a mechanical problem. He popped out his buffer spring and compared it to a spring out of another broken-in AR. He said his is about 1/2" longer and has less coils and has thicker wire. And when he borrowed the spring, it locked back after every last shot. I opined that the other spring is shorter because it's seen a few hundred shots and his will probably be shorter and lock back after a few hundred shots... He was unconvinced... 
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Spring set is one thing, but does sound with the larger coil spring wire to begin with, his spring has more tension to begin with, any maybe even after set.
If the weaker spring is working for him, then let him run with it. How knows, the other rig may run better with the stronger spring instead. |
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The shorter spring came out of another member's AR. Don't think the other guy would give up or trade springs because his is running perfectly. Problem is, what spring to order...No one lists their spring as reduced power. And owner of the spring built his AR and doesn't know what brand or where he bought that spring.
And forgot to mention that I had suggested that he leave it cocked for a few days. Still failed to lock back occasionally... |
| i just finished putting together my first ar15. i have shot about 50 rounds of wolf through it so far, and the bolt has failed to stay open twice. im glad i found this post cause i was a little concerned i didnt put something together right, but it sounds like it just needs some break in time. it has also failed to pick a round up a couple of times is this because of the same thing jsut needing to be broke in. thanks guys |
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