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Posted: 11/18/2013 2:26:46 PM EDT
I built an AR/M4, I have a Medcon M4 milspec upper 16" heavy barrel 1:8, an American Tactical lower, DMPS trigger/hammer and springs MagPul 6 position stock, buffer and spring for carbine, XTS picatinny quad rail, have two new Tapco 5.56 milspe3c mags, am using PMC bronze .223 remington cartridges. When I put in the mag and cycle the charging handle everything seems fine, I fire the round is ejected, then next round is stripped from the mag and chambered, but when I squeeze the trigger the second time the hammer is not cocked. Ive taken the gas assembly completely apart checking the gas tube and block, the bolts gas rings are aligned so that the slits are in different places, I even took the lower in my lap holding the bolt carrier assembly at the approx hight above and ran it back by hand and the hammer cocks, so I'm kind of at a loss as to the problem. I am no stranger to AR style weapons, spent 4 yrs in the corps 8 in the Navy, 7 in the Army, 4 combat zones and have fired and field stripped and cleaned everything from M16A1 to A4, but this is my first build. I've also purchased an AR15 amorers course from AGI hoping that it would help to shed some light on what the problem may be, but I don't see anything that would cause this problem. I trouble shot the trigger/hammer/sear first thing but all is fine there. Any help would be appreciated. 
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| I am not a gunsmith so please forgive me if this is off but it sounds like the disconnector is not working. I know you tried it by hand and all seems ok but I had a problem similar to yours and found the lighter disconnector spring I installed must not have been fast enough to catch the hammer and the hammer would follow the bolt home. My problem drove me nuts till I swapped lowers and the trouble went away then I started swapping out parts -- hammer and spring was no help, trigger group fixed it -- so then I swapped trigger group parts to see what exactly it was -- turned out it was a light pressure disconnector spring I got with a spring set for shooting with a 22lr conversion. I honestly don't think your rifle is short stroking since the bolt/carrier is traveling back far enough to pick up and chamber a round ok. I could not duplicate the problem I had by hand cycling -- everything worked just fine that way. I had to physically go to another lower to prove what was causing the problem. This all happened with a rifle setup that worked 100% prior to my swapping out the springs for shooting with a 22lr conversion. I'm not saying it's the disconnector spring in your case -- just something wrong with the disconnector. Maybe somebody here can give better information on how to check if it's a disconnector problem or not. |
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Could try some higher powered ammo, PMC Bronze is about the weakest factory 223 you can buy, so it's possible that it's got a short stroking problem.
Disconnector or disconnector spring is the most common cause of your symptoms so probably good to give them a careful look or even swap out to other parts if you have spares available. |
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