6mm bullets over 300 yds? Sure, I killed my longest deer kill w/6mm BENCHREST, 105 amax, double lunged, deer stumbled 25 yds and dropped.
OP, Hear Federal will load 85 TSX, it will go thru any deer bone and kill elk as well-and has.
My BR shot 2840 mv. Factory 100 gr Rem shot 2800 in 20" RSI #1 Ruger, SO reloads are better than many factory that are 'under spec'd"
Reload and want more thump, 260, factory ammo - need more choices, go 7/08.
In a 243, my fav bullets are 85 Tsx and 95 ballistic tip for deer. Both work great. Partitions make a narrow wound channel in my experience. 85 BTHP and 87 SP and BTHP will kill fast on broadside lung shots, but back to my fav bullets, any angle you can reach vitals, and do it past 300 yds.
I shoot 6BR, sold all my 7/08s but do have a 260 and 6.5x55, go to bullet- 130 accubond. Perfect conditions, if I know how far/where to hold, I'll shoot the BR to 400 yds again, maybe further but not over 500. The 6.5's, 500 yds no problem.....for killing power......my ability.......depends on conditions, recent practice, shot opportunity, etc.
BUT suffice to say, MOST deer show up/die under 200/250 yds, but I want to be prepared if a shot presents and conditions inc. my nerves are up to it, I know my load can get it done. Normally 400 yds is my self-imposed limit.....again, under ideal conditions, less than ideal, 250-300 is a long shot.