Trying to make sure I know what someone should know about A1/A2 receiver extensions / buffer tubes for rifles.
I've seen comments elsewhere that mil-spec for rifle receiver extensions is 7075 with rolled threads.
Obviously, 7075 is going to be stronger (~2x) than 6061, so I'd rule out 6061.
Not everyone understands this, but I'm enough of a fastener geek to know that rolled threads versus cut threads is actually a yuuuge deal. If TDP specifies rolled threads, then presumably a Colt tube has them. And the aftermarket being what it is, it's extremely unlikely any other manufacturer is bothering. Which would mean no other part really comes close.
It's been years since I looked at @
rob_s' list; I don't remember it dealing with rifle stuff, but I was focused on carbines at the time.
TLDR: If I want the best rifle-style receiver extension, I just buy a Colt tube and roll on, right?