Did some shootin yesterday with a new 870 SuperMag for first time. I had been reading about this gun having problems with jammin up on 3.5's, so I was worried about it.
I found a couple of boxes of Rem 3.5/12/2.4oz. magnums for 12.00/box at Dhams , so I tried one on the first shot. YEP...she jammed up and had to really work at gettin the spent shell out, but did. Then I went to a Hevi 13 same size etc.. and no jam. Second Hevi 13 no jam up... but I didn't get the chance to go back to the Rems. Had too many issues with the red dot, so we quit for the day,and will go at it again on Easter sunday.
