I have an old m500 with the factory full choke. I use Remington 3" 1 7/8 oz shot , 4 shot, Nitro Magnum's with very good results. I have tried other brands and load but nothing patterns better than the shell i just mentioned. I call it my killer gun. I have never had a turkey get away that I hit. I have missed a few though. Not getting down on the rib, ya know.