My dad has a BAR in 338WM. Off the bench it beats the crap out of me (and recoil doesn't usually bother me). If you get one, get one with the BOSS on it, your shoulder and retinas will thank you.
Accuracy is about 1" or so at 100 yards. It's a great gun in the woods, I'm not sure about the long range accuracy potential of the rifle.
I keep nature balanced - I hunt everything!
My dad had one in a .338 WM and shot the Federal 210g Partitions. It grouped 3/4" at 100 yards. He took a couple spike elk with it, and one was 500+. The recoil is not that bad. Its a semi auto, it soaks up quite a bit. I dont think you'll need a BOSS, but obviously you said you want one. My dads did not have the BOSS and we had no problems getting 3/4" off the bench. Another note, one of my elk hunting buddies has shot a 300 WM in a BAR for 20+ years. He has shot a bull every year with it. It is also very accurate and has taken elk out to 600 yards. Browning BAR's are very nice rifles. You wont go wrong with either.
Unless they've changed them the boss is terribly loud. I had a 270 win with one and I thought it was louder than my 300 wby with factory brake. I can't figure why these factories have to port the sound and blast back at the shooter instead of straight out the sides.
Usually shooting in the field the sound of my 300 wby is absorbed but the crack on my boss equipped .270 left my ears ringing. My gun was terrifically accurate and if I'd have known they were coming with the crf I wouldn't have sold it. Just my $.02 cents worth.
Yah I second that the Factory brakes are RIDICULOUSLY loud. Just like the above poster, I seen a guy come with a .270 with the BOSS, the thing was like shooting a 300wizbangsupermagloudenboomer. I could not believe it. I had my 25-06 with my muzzle brake from score hi gunsmithing, and it was no where near as loud. I guarantee it.