Jordan who shoots at ASRA is modifying ARs with .22 uppers to account for that.
He fills in the slot at the back of the magwell and then removes the corresponding ridge on the Blackdog type mags. Basically they become the S&W style mags and magwell.
So normal AR centrefire mags won't fit the lower.
He also permanently blocks the buffer tube with an alloy plug. No buffer and spring can be inserted and no centrefire BCG can now cycle using that lower.
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