having an issue with my shotgun and dont know what it could be. today i went shooting to sight in and just have a good time. the .270 zeroed well, but i had issues with the shotgun all day. id shoot, get a good grooping, but not on target. move the scope, shoot again, and get another good grooping but not were i expected it to be. i spent about 30 shots chasing the groops around the target. then i took a break, and drove 1/2 way home and stoped in at another range. took 3 shots, got another good grooping about 3 in under the bullseye. then figured id do one more groop of 3 just to varrify, and again got another good grooping, but this time about 15 inches below the groop i had just shot. (and i did not make any adjustments) what could be going wrong?