Light Strikes on 300 BLK AR-15
- Thread starter KentM
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mcb
Member
If the firing pin looks OK then look to make sure your fire control is not damaged or otherwise compromised by dirt and debris. Give special attention to the hammer spring, make sure both legs are present and that it is installed correctly. Make sure the hammer is free to move on its pivot. Also be sure the firing pin channel in the bolt is reasonable clean and no debris present.
Blue68f100
Member
Sounds like it's not going fully into battery. Clean up the barrel extension nut/chamber and bolt real good. Also check the gas piston area of the BCG for carbon build up. This can prevent the bolt from going into full battery once it's gets carbon up. Shooting subs can make this area real dirty.
BBBBill
Member
^^^^ Check what Blue68f100 said first. Could also be a combination of marginal firing pin protrusion, generous headspace, and/or variable cartridge dimensions. Easy measure all.
Armorer 101
Member
When the bolt fails to lock up, the AR stops firing by design. The tell tale sign is the light firing pin strike on the unfired cartridge caused by the disconnect, correctly, capturing the hammer before it can fully strike the firing pin. If you have a failure to fire, with the dimple, look for why the bolt did not lock up, first. The hammer and disconnect are working correctly, so you have bad ammo or crud in the chamber and/or bolt recess, clean the gun with an AR chamber brush and check the ammo for bulges, bends, length. Just pull the take down pin and pull the bolt, clean, inspect, clean again.
The AR-15 must be kept clean, it craps where it eats, feed it good stuff!
The AR-15 must be kept clean, it craps where it eats, feed it good stuff!
greyling22
Member
If you can, put the upper on a different lower and try it out. Might help pin down the source.
The Glockodile
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- May 6, 2020
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Incorrectly installed hammer spring!
Common oversight when installing (aftermarket) trigger groups...
Common oversight when installing (aftermarket) trigger groups...
Pull the bolt/check the firing pin protrusion when you push the pin fully forward.
I like 30-35 thou as a general rule.
If that checks out, the hammer is "unlikely" to the problem.
Since it's factory ammo, cartridge headspace ("dimension" for the purists) also "unlikely" *
Check that barrel extension nut/chamber/lugs for debris preventing complete bolt rotation
* if all checks out, have a smith see if the chamber headspace is really tight as it came from the factory.
(Or just fully resize (cam-over)/prime a few empty cases... feed by hand/let bolt go home and see it they fire normally)
(... and light a candle to St Stoner for a safe design)
.
I like 30-35 thou as a general rule.
If that checks out, the hammer is "unlikely" to the problem.
Since it's factory ammo, cartridge headspace ("dimension" for the purists) also "unlikely" *
Check that barrel extension nut/chamber/lugs for debris preventing complete bolt rotation
* if all checks out, have a smith see if the chamber headspace is really tight as it came from the factory.
(Or just fully resize (cam-over)/prime a few empty cases... feed by hand/let bolt go home and see it they fire normally)
(... and light a candle to St Stoner for a safe design)
.
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