I think Trailer wants to know the optimal point blank range for his gun. Maybe I'm wrong though.

If that's the case, first you have to settle on your ammo. Once you pick the slug you will hunt with, I would site it in so it is never higher than 3" above the line of sight. That should give you a point blank range of at least 100 - 125 yds.

I would do my accuracy testing of different brands of slugs at 50 yds. to limit aiming error and wind effects. All things being equal (even though they never are) just multiply your 50 yd group size by 2 to get a good idea of what your groups would be at 100. I always go with the fastest slug that meets my accuracy requirements which for me is a 5" 100 yd group of 5. All my shots at deer seem to be at 75 yds and under.