Quoted:
Is there really any way of determining if a buffer tube is 6061 or 7075, other than the sellers say so? I know 7075 is preferred, but I'd think 6061 should be fine unless you plan on butt-stroking trees - in which case both might prove inadequate.
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Buy it from a reputable vendor. A quality vendor will have quality sources that will supply exactly the product they say they are.
Yes, from a range commando perspective there should be no real difference in performance. But a few things typically go along with the 7075 alloy: they’re almost guaranteed to be MIL-SPEC extensions.
MIL-SPEC receiver extensions are made to MIL-SPEC dimensions held to tight tolerances, they’re made with known production processes, they have high quality coatings, and rolled threads (which are tougher than cut threads sometimes found on lesser extensions).
So long story short, buy a MIL-SPEC receiver extension from a trusted source and you’ll get all the positives that go with MIL-SPEC, including the right alloy.