Hey gang,

Been all around the site & Internet looking for this: A1 & A2 rifles--what alloy is a mil spec rifle have?

I'm guessing 6061.

Reason: I'm building a retro A1 from a Colt kit & have an A1 kit receiver extension & an A2--they're the same length. If one is more durable than the other, then I'll save the other as a spare.

Thanks for the help.

7075....

Any idea for how long it's been used?

I've read that 6061 was used in the 1960s upper & lower receivers, then were switched to 7075-T6 mid-1960s. Based on 6061 being easier to machine, I thought that's what's being used.

I've contacted multiple companies on the matter later yesterday--too soon for a reply.

When I look up receiver extension/buffer tubes--the carbine alloy is listed--but not the alloy used in a rifle WTF?