DD, I don't shoot over 400 yds, but if I had a load getting 2700 w/120, I'd let lead fly up to 400 on a deer if broadside. Ran #'s, looks like a 200 yd zero at 3,000 MV drops 19.3", if started at 2,700, it drops 19.7" at 375, so basically you lose between 25-30 yds of PBR according to my #s.
Flat is relative to many things, but ALL bullets drop, and it's the shooters responsibility to be prepared to KNOW where the rifle will hit whenever leveling down and about to squeeze.
At 2700 mv, the 120 BT has 1,046 lbs. Plenty. My 6BR using a 105 at 2850 has 1093, and I did kill a deer fine w/it (LRF right at 400 yds), went maybe 20 yds after a double lung hit/exit.
Many bullets will/can blow on a knuckle, esp. at close range.
I agree a longer bbl is preferable, a 23 vs. say a 26 IMO is ideal for handling, maxing powder burn, lowering blast. Smaller the caliber, the longer the tube needs to be all else equal to get the powder burned. 26-30" 6.5s can really p/u some speed if one is needing it for long distances.
Lastly, IIRC, lighter bullets lose more speed than heavies in shorter tubes. If so, then a 129 gr might be a good compromise, if not the 130 Accubond, tad more drop, but heavier hitter downrange, but that variable is determined where/how one hunts.
