First thing I would do is clean the shotgun thoroughly, and make sure it's chambered for 3" shells. If it is use the Hw #7's, or the hevi-13 #7's, cause those are probably Gona give you the best pattern with a mod choke. I have an older Stevens 94 20ga. with mod choke, and last year I fired one round at 40yds to for quriosty, and it shot 76 in 10" at 40yds. I wished I had tried it at 30yds, cause that would be max for that shotgun. I would have him fire several rounds at 20yds with game loads just to get a feel were the shotgun is shooting point of aim, plus a little trigger time never hurts.