I would at least shoot 3-4 shells at 100 yds. to see how your rifle shoots with them. IMO I would want to know where those bullets hit after all to put all the work into finding a big buck then blow the shot because your gun isn't sighted in can have a tendency to make you want to kick yourself in the rear. Good luck on your hunt.

always shoot your gun after you change ANYTHING especially ammo. Never go into the field with an un-proven weapon. It will probably be pretty close to being right on if you shoot the same weight but it's also something you don't want to leave up to chance.