Six, half dozen the other for deer. If choosing the 6.5, I would stay with somewhat lighter cup and core bullet for deer. I took two deer with the 6.5 140 grain accubonds that did not open up much or leave much of a blood trail. Both deer recovered, but it took some tracking. Both double lung shots. Never had any trouble with 6.5 or 7mm cup and core like Hornady Interlock etc.
Use one that will open up. 6.5 140 grainers are long bullets and will hold together. I don't think they need to be bonded or mono- metal on top of that. Nothing in any chambering I have has given the same level of quick kills with great penetration as the oft maligned 140 Gamekings out of my 260 Rem. I went to 120's because I thought my slower twist demanded it - despite my lying eyes. I have used various 120's with good success but the 140 GK to me is perfection. Going back to them.
