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Posted: 5/22/2007 4:13:15 PM EDT
| I have an AR-15 with a 10.5" barrel and collapsable stock. Every 10 or 15 rounds wont' fire, but inspection of the manually ejected round shows a dimpled primer and it'll fire when I put it back on the stack. Naturally, have duplicated the problem with several types of ammo. Any ideas? Thanx in advance for your expertise! |
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Light primer strikes caused by worn/light trigger spring, or light hammer. possible firing pin probem, but I think prob something else. Need more info about your SBR like FCG setup, How many rounds have been through this rifle, is it new, anything new/changed 9mm, 5.56? |
| It's a PWG lower with no-name barrel. The lower is a pre-ban and has always fired .223, as far as I know - bought it used. Trigger changed to comp or match - very light. Changed the barrel from 16 to 10.5. Tried standard and chrome silicon buffer springs, as well as std, H, H2, & H3 buffers. Changed extractor spring to chrome silicon. I've personnally put a few thousands rounds through it, and it's probably had tons more before my time. When I bought it it had extraction probs, which I fixed with the new buffer and springs. It also had this firing pin issue that I'm still trying to resolve. I haven't done anything with the hammer. |
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Bolt bounce, Hence the carrier is not being controlled by the buffer at closing, and the carrier is bouncing off the barrel extension backwards at the time of hammer release/strike to the FP with the back of the carrier blocking the FP, preventing FP protrusion out of the front of the bolt. Normally a heaver buffer (H2/H3*, SMG, or MGI in that order regarding more mass/weight) will solve the problem, but you need to check sear release as well. Is the lower a M-16 with a convention sear, or a RDIAS/RLL being used in a host receiver instead? The reason that I ask is in regards to the cycle rate you are looking to achieve. On shorter rigs, I tend to Mac-jack them for a cycle rate around 1200RPM with a tuned Branson type brake {quick bursts with the muzzle holding steady, them move onto the next hard target). If this is not your style, then the slower rate that the MGI buffer will produce (in the 700 range) may be more your style if you are prolong bursting/mag dumping with a standard FS. www.quarterbore.com/ar15m16/index.html www.biggerhammer.net/ar15/buffers/ *A standard carbine type buffer has three internal discs/sliding weights to create dead blow effect at end of action cycle. On the H-2, two of the discs are tungsten steel, with the last disc standard steel to add additional weight over that of a standard carbine buffer. On the H-3, all of the discs are tungsten steel for even more weight. Also to point out, the internal weights are free to move at will depending on the angle of the rifle with the standard/H buffers. This point is mute in regards to your rifle since it is a gas action unit, but in regards to a blow back type action, the SMG, or MGI buffer with the weights spring loaded forward will insure that the mass is being used to it fullest to slow down carrier at movement of ignition. |
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I originally had a feed/extraction problem that I solved with a new buffer spring, extractor spring, and heavy buffer. When using H2 and H3 buffers, I still experience the firing pin problem. I can' answer your question about the sear, 'cause I've never dealt with this part. Give me some time to find and inspect it. Many thanks for your input. |
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