The problem you have with subsonic ammo, or in your comparison, pistol ammo is the lack of terminal damage. A bullet hitting at over 1,000 lbs of knockdown power at 2,000 to 2,500 fps (at close ranges etc) is doing a lot more damage than a 30, 33, 45 caliber lead just punching through something. The displacement of tissue etc is is the big difference.

That said, a buddy of mine had shot deer with the same setup your referring to. 7mm I believe. Running a heavy bullet in a fast twist barrel. Has had good luck but only used on close shots to test and has supersonic ammo with for longer shots. He was just testing and knew the zero of the subs compared to the regular ammo.

If you want to try it I say go for it. Keeping those thoughts of knockdown power and range in mind. If you hunt close it isn't a real issue. Where I hunt your shots average 200-300 yds. Obviously outside of subsonic ranges.

A well placed bullet will kill literally anything....but so can a well placed rock