A 155 grain bullet will do the jobfor deer IF the velocity is right,he bullet is constructed for hunting, and the range is appropriate for the velocityh and bullet construction(the 150 grain 30-30 is a proven deer killer).

You would need to do a little research on the bullet and be very disciplined in using it for hunting with a muzzle loader.

Why limit yourself when there are so many really good heavier bullets available?