A couple observations from my experience with H&R .410's...If you don't have a "tall" front bead to compensate for barrel taper you're probably shooting high. If you're shooting 3" shells, try switching to 2 1/2" shells for a few rounds, they pattern better for me. At 25 yards you are at the correct distance to pattern .410"s but you may want to start at closer to 18 yards to get a feel for sight picture/patterning shot etc. The .410 for me is a short range affair, patterning at different ranges is imperitive to knowing your own limits as far as shot size and capabilities. YMMV
Good Luck!
Scott B.
Mossberg 500E .410, Sears Ranger (Stevens) 37 in .410, Marlin 200 in .410, H&R Pardner in .410