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Can anyone help me check the headspace on my P90 clone? I received a 10.5 inch CMMG and my Form 1 for SBR has been approved. I took it to the range and it is not cycling. The shoulders on the rounds are blown out. I think I have a headspace issue but do not know how to adjust or measure for it. Thanks

Ken

Brand new CMMG barrel? What rounds are you firing? What adapter did you use to affix the barrel back into the receiver? Did you remember the spring in the receiver? How tight did you tighten the barrel?