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Posted: 6/16/2010 6:43:11 PM EDT
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I put together an AR featuring a used upper and BCG from the EE, on a Sabre lower with a Delton parts kit. Took it to the range last weekend to function test it with a box of federal bulk pack 55 grain .223 ammo - the 100 round boxes they sell at walmart. I got numerous failures to fire - some of the rounds fired on the second primer strike, some didn't. I'm wondering - did I get a bad box of cheap federal ammo, or is there something I should check dimensionally on the firing pin, or maybe not getting enough energy out of the hammer? I'll test it again this weekend with some different ammo, but I'd appreciate thoughts on what else I might take a look at. This is the first lower I put together without having a detailed set of instructions - I passed on my AR-15 assembly book with my last AR when I had to sell it due to my divorce, and put this one together based on the instructions here in the build it yourself forum, so I don't think I put the hammer spring in wrong, but who knows. Input is appreciated.
I can take pics of the lower assembly if that will help, and maybe I should be posting this in the build forum, but let me know. Thanks. |
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I would say look at your hammer spring and make sure it isn't in upside down. Also, take a look at the end of your firing pin and make sure it looks good. Then make sure your bolt and carrier are clean and lubed. That's where I would start. ETA: arms of the hammer spring should be coming off the bottom. |
| It could be from installing the hammer spring incorrectly or from having a light spring designed to reduce trigger pull weight combined with hard primers. It could be the firing pin as well, if the tip is damaged or doesn't protrude far enough it could cause failure to fire. When the gun doesn't fire are there dents in the primer at all? If so, do they look like good strikes or light strikes? Does the primer strike on unfired rounds look the same as on fired rounds? Pics of the fired and unfired rounds as well as the FCG may be helpful. |
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Quoted:
I would say look at your hammer spring and make sure it isn't in upside down. Also, take a look at the end of your firing pin and make sure it looks good. Then make sure your bolt and carrier are clean and lubed. That's where I would start. ETA: arms of the hammer spring should be coming off the bottom. Looks like my arms are coming off the top, rather than the bottom of the loop. I'll take the lower apart and reassemble. Thanks. |
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Quoted:
Quoted:
I would say look at your hammer spring and make sure it isn't in upside down. Also, take a look at the end of your firing pin and make sure it looks good. Then make sure your bolt and carrier are clean and lubed. That's where I would start. ETA: arms of the hammer spring should be coming off the bottom. Looks like my arms are coming off the top, rather than the bottom of the loop. I'll take the lower apart and reassemble. Thanks. I had the same thing, and then did the same thing, I'm willing to bet that it was the problem. Mind wouldn't fire at all though. |
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I'll range test it tomorrow. Thanks ARFCOM!
Need to add that pic of the correct orientation of the hammer springs to the "How to Assembly your lower thread" since it isn't obvious. It was called out in the book I had, I think by Clint McKee and Walt K. Unfortunately, I passed the book on when I sold most of my AR rifles and parts thanks to the shitty divorce I'm still working my way through. |
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