Depends whether you meant 'best deer' or 'best deer shot' (emphasis on 'shot'). My best deer was a 300 pound Whitetail buck in south western Manitoba. One shot with a Browning 1886 saddle ring carbine 45-70 using a 350 grain Hornady round nose loaded to 1,850 fps. My best deer 'shots' were two large Whitetail does taken at 185 yards offhand with two shots from a Winchester/Miroku 1886 extralight 45-70 using a 420 grain cast bullet loaded to 1,350 fps. Runner-up for best 'shot' was a Whitetail buck running flat out at 75 yards broadside to me. One shot (aiming about 3 feet ahead of the buck) with an original Winchester 38-55 using a 255 grain cast bullet at 1,400 fps.