Good vid, 5*'d. I use the 870 + 12 gauge + mag ammo combo a lot, and even though I absolutely adore it, I've found that the hitreg is really iffy at times. I never gave much thought to standing relatively still while taking the shot, but I'll keep that in mind while rambo'ing around and see if it helps.
The worst case of bad hitreg I've had was when standing completely still behind a crouched and totally still enemy about 5 yards away, just out of knife range, my shotty was aimed square between his shoulder blades, 2 rounds shot - no registry, 1 in the head - again, no registry, he 180's and pops 1 M1911 bullet into my head. In my younger days, that sort of stuff caused my keyboards to have a short life span, so it's a good thing for my keyboard that I've mellowed out in my older-age!