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Posted: 12/28/2006 12:29:30 AM EDT
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This is my first AR. It is DPMS 7.62X39. I shot the gun last weekend and it was jamming like this on the picture. Also sometimes it won't pick up rounds from 10 round plastic mag and closes on a empty chamber. Very inconsistent feeding. What might be causing this problem? What I am guessing is short-stroking. Any thouths and possible cure? http://i57.photobucket.com/albums/g211/Nyamdavaa/IMG_0360Medium.jpg |
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The short stroke test is to load one round in a mag, insert the mag into the rifle, charge the rifle and fire the round. If the rifle locks back on the empty mag, then the gas system is working correctly. If it does not lock back, try another mag. If is still does not lock back, look at the gas key, gas tube and look for an A2 screw installed in an A1 stock. Once all those variables are checked, then you can try lighter buffers to see if that fixes it. If a lighter buffer makes it run, then you can open up the gas port. 90% of feeding problems in the AR-15 action are magazine related. |
They are also known for eating bolts. Some of the Frankenmags are known to work okay. Colt bolts seem to live the longest so far. Of course every manufacturer will say its only the other guys bolts that give problems. And their mags never jam either. M9 |
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Thanks guys, I'll shoot some more this weekend and report back again. BTW, here is the pic of the whole setup. http://i57.photobucket.com/albums/g211/Nyamdavaa/IMG_0326.jpg |
Did'nt know that, then again I don't own a 7.62X39 AR either. |
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FWIW, I have an AR in 7.62x39 and your problem is very similar to the issues I was having with mine, it was all mag related. I found some 10 round metal USA mags on gunbroker that seem to function pretty good with 8 or so rounds in them. ETA: Purchase or borrow a standard AR (223) mag and just load 2 or 3 rounds in it and try that also. And, lots of good folks here on AR15.com with good advice, so just keep working at it till its running right. |
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The short stroke test is to load one round in a mag, insert the mag into the rifle, charge the rifle and fire the round. If the rifle locks back on the empty mag, then the gas system is working correctly. If it does not lock back, try another mag. If is still does not lock back, look at the gas key, gas tube and look for an A2 screw installed in an A1 stock. Once all those variables are checked, then you can try lighter buffers to see if that fixes it. If a lighter buffer makes it run, then you can open up the gas port. 90% of feeding problems in the AR-15 action are magazine related This is the guy who helped me with my AR Short Stroking problem. After everything was cleaned and checked it was the Carrier. What I finally did was swap bolt assemblies with a bud. His was Colt my rifle was Bushmaster. The Colt bolt and carrier in my Bushmaster shot flawless however when I shot Radway ammo it short stroked my 16" carbine again. I swapped for his 20" Colt upper and the Radway shot fine. I know this is 6.8spc forum but maybe I help with this. It took me weeks to swap and try different things until I narrowed the problem. I don't know if they sell a D ring for your extractor or you need to adjust your magazine height or buy a new bolt and carrier assembly from Colt. I would say first see if you can swap with somebody using the same cartridge then start the process of elimination. Here is what I did: Different Buffer Different magazines Different recoil spring Checked magazine height Cleaned gas tube and check gas hole spec Cleaned carrier key Checked carrier key screws Replaced gas rings (did not have to use D ring on my extractor) Checked stock made sure recoil spring housing hole was clear. Tried different ammo Swapped bolts, bolt carriers, and uppers. Checked trigger for drag Narrowed down to the carrier. Fixed |
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