AR Question

truckemup97

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CDNN had a pretty good deal on an ATI .22LR upper, so I bought myself one for Christmas. I put it on my New Frontier lower and it doesn't fire. Not even a mark on the casing, so I'm guessing that the hammer isn't hitting the firing pin actuator. (my terminology may not be completely correct) When I put the ATI upper on my S&W lower, it fires just fine. The NF lower works with my PSA .223 upper. So each piece functions as it should, but the NF lower and the ATI upper don't work together. What's going on? How can I fix this? I would rather leave the S&W together and use the ATI upper on the NF lower. Any ideas?
 
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Take a look at the hammers on your Two lowers.
I'd be willing to bet that the NF hammer is one of those with a cut out at the top and the ATI .22 bolt has the firing pin at 12 O Clock.
Equals no way the hammer can make contact with the firing pin.

ETA:
you can fix it by changing out hammers to a rounded top like on your S&W.

hammer.jpg
 
Last edited:
It does look shorter from pin to top length than a standard AR hammer.
Doesn't look tall enough to hit the firing pin on a rimfire.
Also, is it a polymer hammer?
Sorta hard to tell in that pic.
 

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