caliber choices

[chet]

I presently have a 6BR with an 8 twist 28' Pacnor and it shoots the Sierra 107MK excellent, will not shoot the 105AMAX bullets, was hoping to get them to work for long range groundhogs, so I am down to ordering a new Savage LRPV rifle either in a 6BR with the 12 twist or the 22-250 with a 9 twist, which of these 2 calibers would be better for long range groundhogs, 800 yds plus and what bullet will make the flattest trip there, Like I mentioned earlier in the message, I was hoping to get the 105Amax to work with a 6BR 8 twist and it did not happen. right now I am shooting a Savage 223 with a 9 twist model 12bvss-s the load is the 75 AMAX shooting at 2955fps with EXTREME accuracy.so my question on the caliber choices would have to outperform the 223 75gr AMAX performance 2955 and the high BC combination.

thanks
Chet