Richard wrote:
On 4/8/2013 4:06 PM, Ed Huntress wrote:

Snipped - just to show it's technically possible...

Something is strange there. I'd have to dig out my ASM book to check,
but 7075 has low corrosion resistance overall and is not recommended
at all for marine environments (or salty sweat, one would assume).
6061 is somewhere in the middle.


I wondered about that too.

What's the story here?

Current Mil spec is 7075 - T6

The original design called for either a 6 or 7 series alloy. The 6 was
cheaper and easier to work with so that was what ended up being used.
The problem is that between corrosion and thread deformation the spec
was re-written to 7075 - T6 being the "correct" alloy to use.

I have shot both and other than knowing the alloy due to the makers you
couldn't tell any real difference. 6061 is still used by a few companies
and with the design of the AR the strength in Civilian use isn't an issue.

However if you plan on needing to depend on the rifle in real combat
where you may be using it as a club, hammer or whatever, the 7075 has
the edge with regard to wear and tear.

I have used both forgings and solid billet as a starting point.
With forgings you are limited as to what you can add/subtract.
With billet you can have fun. I machined in a solid trigger guard,
milled my logo in 3D on the side, and a few other tricks.


--
Steve W.