I have a couple of mills in my shop, so I love the 80% lowers! I would like to make the 6.5 (I have a Sweedish Mauser in 6.5, and I LOVE IT!) Grendel. because it is balistically sound, and an excellent choice for this frame! I run an M14 for the punch, so I will avoid another calibre on the 300, even though I hear it is excellent. I have thought about the larger sizes, but I wonder if the design is up to that much more stress.
I have heard horror stories about building to 308, and having stress failures; but I find myself questioning their abilities, and wondering if that is the source of the failures.
RE: How to Duracoat your firearm