As Dave in WV mentioned, the Remmy pumps stretch recoil a bit. I'll tell you first hand that I've shot stout handloads in 30-06 out his (now mine) 760 pump and it hurt! Here's what I have found:
Get the gun as high as you can off the bench. Use sandbags, gun cases, whatever, to get it to where you are about as straight up sitting as possible. Have the gun pulled to you and not leaning as much into the gun. You'll roll with it more and not take as much of a beating. The higher you sit, the less it'll bother you. Same as being straighter up instead of hunkered down. Make sure that the butt is well in the shoulder pocket each and every shot. Take a 22LR with you to fool with between shot segments. Above all, be honest with yourself. No when you've had enough. I'm sure we've all been there and have pushed the envelope but then you're not doing yourself any justice. Good luck.
Chad