my friend JACK in Colorado used his 450 marlin caliber BLR loaded with a 405 remington bullet over 50 grains of IMR 3031 last season, I don,t have pictures but he stated range was about 170 yards and the elk he hit behind the shoulder dropped withing 10 yards of being hit, bullet passed thru , he was very happy with the result.
I used the same load in my BLR and held under 1" 3 shot 100 yard groups off a solid bench rest at 100 yards

IVE used a 45/70 loaded to similar, but slightly lower velocity levels in the past and it killed elk very effectively.
the 45 caliber rifles work really well with the 350-405 grain bullets I would not be looking to use anything much lighter as you can do that with a flatter trajectory and less recoil in a smaller caliber, the 458 diam. has advantages if used with the heavy slugs,and one is deep penetration and an impressive wound track if used with the correct bullets

Last edited by 340mag; 05/19/12.