I know you're not looking for factory ammo info, but I use Federal 100 grain ammo from Walmart ($14 for a box of 20), and typically get less than an inch at 100 yards for three shots.
I have done a bit of reloading, and am using Hornady interlock 100 grain bullets, part number 2450. Using 39.5 grains of H4350, I have been getting 3/4" groups at 100 yards.
This is with a bull barrel.
Good luck.
Tim