Shot my 870 super-mag yesterday with my FF III 3 moa for the first time. Works great! I have a B-Square mount for now. Mounted the FF, put gun in lead sled, looked under the b-square and alined the bead on the bullseye then move the dot to the bullseye. First shot (3.5" win XX 2oz #4) was slightly left, made the ajustment and moved to 40yds. Moved pattern up a hair shot again and it"s dead nuts! Thanks to this sight I'm a happy camper!