The receivers on the Armalite are made of 7075T6 aluminum, while the DPMS are made of 6061. Bushmaster/Remington do not specify which alloy they use in the .308 AR models but they do specify 7075 for the AR-15 (so does DPMS, BTW.) SO this leads me to believe that Bushmaster uses 6061 in their 308 ARs, unless somebody can point me to a Bushmaster link that says otherwise.
To me, that is a BIG differentiator, which is why my planned AR-10 build starts with Armalite receivers.
Why do you care what alloy they use? I asked Jason at Quentin Defense about it. He told me that in a billet lower there was no reason to use anything other than 6061 T6. He said that 7075 was used in some AR 308 platforms that used FORGED receivers as it can be forged. He said that the strength is a non-issue as there are plenty of PLASTIC lowers out there! I thought that was a pretty compelling argument to use 6061.
