The only 125 grain .308 bullet listed in the Speer manual is the TNT which is a varmint bullet designed to give rapid expansion, not penetration. In other words you are going to have a wounded deer on your hands. I think Sierra makes a 125 grain bullet suitable for deer but I' m not sure. Personally I don' t like Speer bullets anyway. Always found them to be fragile. As to your comment about deer being killed cleanly with a 55 grain bullet out of a 22-250 Rem, well I have seen deer taken cleanly with a 22 LR but it doesn' t make it wise.