20 gauge 870 fieldmaster question

[Uncle Tom]

Where you holding the bead on the target? I have a 20 ga Fieldmaster with a Burris Fastfire III....never shot it using the bead. But, if it hitting low at 40 yards and dead on at 20, you know where it is hitting at all ranges....just hold on the turkey head where you know it will hit. Now, that probably would not work hunting moving game like dove, rabbit, etc....but a stationary target like turkey just aim high, or get a smaller bead as someone stated.

[LRD]

Have you tried different ammo to see if it is the same?  I'm leaning more towards ammo velocity than gun because it doesn't make sense for it to be dead on at 20 and low at 40 due to the gun.