I was just throwing out a differing opinion.
I didn't know you were intending to stretch it out to 800 yards with a 4.5lb rifle.
I assumed that with that light of a rifle and 16-18" barrel this was a short handy rifle for thicker timber.
Most would agree a 308 and 6.5 Creedmoor are about equals killing wise under 500.
with a 16" barrel your going to be closer velocity wise to a 6.5 creed.
now that your saying you think 19" is what you want to go with that changes everything and I like the 6.5 PRC idea a lot.
please post up the results of your build. I have been contemplating a similar rifle but closer to 5.5-6lb. All my research keeps coming back to might as well go 308 or 7mm08 in that short of a barrel.
(16" is what i want )
I am looking at actual velocities that people are getting between 16-20". I put 16-18" because I have found some beta down to 20" where a guy cut his SAUM barrel with a mild load and 147s but he stopped at 20".
it looks like with 156s
6.5 PRC will definitely get me 2800 fps out of a 19" some are saying I should get 2600 out of a 16" which makes me good to 700 (not sure I am willing to gamble that on a 700$ barrel).
6.5 saum - going to be faster in all
6.5 SS even faster and looks like probably close to 2800 FPS.
I live in Utah and hike a lot which I why I want short/light rifle. 800 yard is my self set ethical distance I will personal shot an animal. I will likely stretch the gun to a 1000-a mile occasionally.
6.5 PRC is going to be cheaper barrel, reloading dies and brass. I didn't think I was going to get 2800 out of a sub-20" barrel.
factory reloads do not matter to me at all, but I guess they will be there.