I've already done due diligence by searching and reading about 2-ply checks. So here's what I'm doing.
Coors Light aluminum 'bottles' and 16-oz cans are .006 thickness.
Using a Pat Marlins Checkmaker, I'm making 1 and 2-ply checks and applying to Lee TL312-155 and GCing and PCing with Smokes clear and push sizing to .311. Also prepped some with Gator checks for a control group.
So far at 50 yards with the 1-ply Al GCs and Cu GCs groups are the same size, same POI from a 12 twist .308 over 22.0/4198. The 2-ply checks (.012) are next up later this week. I'll try to get out to the club range for 100/200 yd testing.
Is anyone else PCing Al GCs? Results?