I have a 450 BM and absolutely love it for close range woods or small field work. I have a 6.5 Grendel, when I get it to run, I am anxious to see how it does. My grendel is a 20 inch barrel, they seem to think the longer barrel helps with velocity.
Ruger makes an SFAR which is sort of like an AR15 frame 308. Had I known about it, I would have gotten one of those. I do have a PSA AR-10, and its really not much longer than my 450BM. It's a little bigger and clunkier, but not enough to worry with.
I will say if you want an AR10, DO NOT get one from Bear Creek.
The best thing about a black rifle for me is how you sling it. Mine are all hands free, and hang on my chest. If you keep a hand on the pistol grip, they come into battery in a flash and are dead nuts silent, it won't slip off your shoulder, and you don't have to carry it in your hands all the stinking time. Biggest issue is you probably don't need to run an extended charging handle.
They have a bunch of options, a 350 Legend would be another option and its pretty cheap as far as ammo goes. I almost got one of those when I got my credit on the BCA 308 upper, but got the Grendel instead, and it won't run ammo either......
