Response provided indirectly from 2A Armament:
It sounds like the parts that you are using may not be correct for your application. It is hard to say without seeing it, but it sounds like your buffer tube is too short or your buffer is too long i.e. a rifle length buffer. We recommend our buffer tube to be configured with a carbine heavy buffer H3, and a Sprinco spring, usually a red spring for .308 applications. This is the way we ship out our .308 rifles. Utilizing this combination should allow plenty of clearance for most carriers to cycle. You are welcome to call us directly to discuss the issue.
Thanks for the inquiry.
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