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Posted: 3/22/2025 6:51:00 PM EDT
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Hello All, I have a unique one off build with a 22 tcm AR-15. I've had it for awhile now, it's mostly worked great and I've put a lot of rounds through it. Everything besides the 22 tcm barrel uses standard 223/556 parts. I have a low mass bcg, reduced weight buffer, and tuned gas block. I recently replaced the full bolt and bcg with the exact same make and model. Curiously, I was having light primer strikes. Switch back to the old bcg and it worked just fine. I took apart the old bcg, and found the firing pin split in half at the rounded joint. Threw the broken firing pin into the new bcg and tested it ... And it works. Any idea how I would even troubleshoot this? |
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Only bolt and FP in hand, insert FP until it stop collar bottoms out on tail of bolt, then messure protrusion out front of bolt face. It should be .032". IF short, make sure back of bolt tail has no burs, then chuck tail of FP in drill or lathe ,and face back the face of stop collar on FP so it does protrude the .032" out of bolt face when it seated all the way against tail of bolt. Now drop just carrier alone in upper, push it all the way forward so gas tube is in carrier key, then tilt muzzle upwards, to make sure that carrier free falls back down/ key is correctly aligned with gas tube. If gas tube needs to be tweaked to index with carrier key, then tweak key over center of barrel, and not where it protruding into the receiver instead. Also, make sure that barrel nut top of spine, or channel through gas nut, is indexed correctly with gas tube channel in upper receiver, so gas tube is able to free float in both the barrel nut, and gas tube channel in upper receiver. If you have binding here, then as B/C goes to lock closed, and carrier is slightly bounced back off barrel extension, it will prevent the carrier from being able to return to touch the face of barrel extension, tail of bolt is not all the way out the back of the carrier, and as hammer strikes the FP, it pushing the carrier closed first, before the FP can protrude all the way out of the bolt. The last one, make sure that the hammer spring is installed correctly,with spring legs out the bottom side, then on top of the trigger pin, and your not getting any binding of the hammer as its traveling to strike the FP. https://static.wikia.nocookie.net/guns/images/a/a0/Fire_Control_Group_Animation.gif/revision/latest?cb=20110429032511 |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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And to add, normal FP penetration out bolt face with stop collar tight against back of bolt tail, should be .028"~.032". The only time you want to increase the amount to say up to .036", is in say 7.62X39 ammo that has harder military primers, or you are running reduce hammer spring tension, or running a speed hammer with reduced mass instead.  And 99% of the time light FP strikes to primer with carrier tight against barrel extension for correct lock up so back of carrier is not blocking FP, hammer spring in the wrong way, and it legs not on top of the trigger pin. https://i.redd.it/7wo9kurnz3sz.jpg |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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Originally Posted By piciphant: sounds like an out of spec firing pin I think you may be correct! I didn't think that it could be the issue. Took the bcg out of my 5.56 and tested it, worked like a charm. Took the firing pin out of another bcg I'm not using, and put it into the new bcg, and it's also working. Looks like the firing pin is indeed out of spec. |
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