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Posted: 3/27/2011 4:24:18 PM EDT
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I realize this is a kind of touchy topic. While testing to see if the jamming issue I was having with my rifle (Spike's upper, Tactical Innovations lower), I ran into another issue. Polishing the feedramps fixed the jamming issue, but let's just say the firing pin is hitting the primer a little too hard when a round is chambered. It never happened when I chambered the first round, but it did happen about twice per mag when using Wolf ammo. It surprised the shit out of me and the other folks on the range. This is the first time I've ever used Wolf ammo in this rifle. It was the stuff in the black box. Finally, I figured out what might be happening and fired the first shot, then ejected the next round. The primer had a very clear firing pin strike in the primer. I should have checked the other ammo I was using, but I didn't think to check it. None of the other ammo slamfired though. What's the fix for this? Should I just not use Wolf? |
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Dirty bolt.
The small indent on the primer is a normal occurrence on any semi-auto firearm with a free floating firing pin. When the bolt slams closed, the inertia allows the firing pin to continue forward slightly causing the dent. Normally the over-travel is not enough to detonate the primer but if the firing pin is sticky from carbon build up or other gunk, it can strike with enough force to set off the next round. Clean your bolt, remove the firing pin and clean firing pin and firing pin channel. Also check for small burrs. |
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Out of the gate, understand the rifle system.
When the B/C is back, and the bolt unlocked, the back of the carrier blocks the Firing pin from fully protruding on the free floating firing pin. As the B/C moves forward to strip a round out for the mag, and the round is fully in the chamber with the bolt now fully touching the barrel breach face, the firing pin is still blocked from protruding, and can not protrude out out the bolt face until the bolt has rotated and the front of the carrier is now touching the back of the receiver extension. Between the strip and the rotation of the bolt, although the primer may be slightly dimpled, there is not enough force of the FP to a standard rifle primer to set it off. But, if the disco does not hold the hammer back with the trigger help back, or the hammer is jarred as well from trigger on the same kind of B/C slamming home, then the rifle will fire. So short of a FP that has broken and now bound protruding out the face of the bolt, the problem at hand is the disco is not retaining the hammer when the trigger is held back. The problem could be as simple as the wrong spring installed in the disco spring location, the correct spring installed but not correctly with the large coil side downward into the back of the trigger rear slot, the disco either sticking open in the trigger or the tail of the hammer too long and bouncing the disco into the open position, the incorrect FCG pin size in play, or even the disco so out of timing that it will not hold the hammer correctly to start with. Go through the lower build one more time,and not only insure that the correct disco spring has been installed into the trigger rear slot under the disco, but the spring has been installed large coil side down. Also, with the lower back together correctly, and the trigger untouched, lower the hammer back until the hammer rear sear the the disco sear are as close to each other as possible. Your looking for a free gap between the two in the .001 to .003 range (about a hair thickness). If the free gap is much greater than this, then the disco will need to be retimed. http://www.ar15.com/content/guides/assembly/lower/ |
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