I am the second owner of a CMMG AR-15 Model MOD4SA
Over the past 100 rounds, I have had a number of problems mostly dealing with extraction, but also with blowing primers resulting in pieces that would get lodged in the Bolt assembly. The extraction issues were solved , but the primer blowing issues still remain despite replacing the firing pin with a new one from Bravo Company.
At the range today, My instructor brought his AR and we compared spent brass. His brass appears normal (including using some of my ammunition (federal XM193) My brass showed a ridge around the depression made by the firing pin on all primers except those that were completely blown through (see attached photos)
Any idea what is happening? Suggestions on repairs?
Normal Spent brass:
My brass:
Worst of my brass today: light strike, heavy strike punchthrough and blowout
My bolt:
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