My continuing saga with PCC

photoracer · Sep 24, 2019

Laj said:
Had the same problem. Tried EVERYTHING and spent hundreds throughout a year. Finally got CMMG to put me on the line with their R&D devision and they immediately had an answer for a common issue. Your ejector needs to be bent inward about 6° using a deadblow hammer.

I had 2 cheap BCGs snapped off the gas block even with 2 screws. So I bought a better Faxon BCG, which has a flat face gas block and that has worked fine.

Mine works fine with aluminum case Federal but I only use it when I can't get brass case.

jimbobborg · Sep 25, 2019

photoracer said:
I had 2 cheap BCGs snapped off the gas block even with 2 screws. So I bought a better Faxon BCG, which has a flat face gas block and that has worked fine.

I'd love to know why the screws break. The only thing they're used for is pulling the bolt.

Magnumite · Sep 28, 2019

jimbobborg said:
I'd love to know why the screws break. The only thing they're used for is pulling the bolt.

1.) Overtorque; 2.) bolts too long/holes or threading too shallow; 3.) incorrect tensile strength bolts.

4.) Also, insufficient contact between gas key and carrier. Bolts in this application are used to apply a clamping load. The parts in contact then have whatever friction coefficient. If the surface contact area is too small then the shear force from cycling will cause the gas key to eventually shear/weaken the bolts. The broken bolts’ appearance will help determine the cause of the failures.

My continuing saga with PCC

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