Thanks bigdog, it's nice to hear from someone who owns a 600 Overkill. I have watched the video from Bijou Creek, and with that load it looks plenty controllable. I'm planning on doing this build without a brake though. Just don't like the way they look. Any thoughts on barrel length? I'm liking the idea of an 18 inch barrel, but might go with a 20.

By the way, what AR site are you talking about? Any input I could get on this build from actual owners would be appreciated. Maybe some reloading data when I get closer. I've seen H4350 used from around 150 to 170 grains. I would prefer to use IMR4350, so hopefully I can just start at around 150 grains and work my way up.