Today I picked up some Winchester large rifle primers to reload some 500 S&W. I looked at the primers and could swear thy where large pistol primers. I thought what the hell and seated one in a used 10mm case. What, it seated perfect and did not stick up at all. I then thought maybe it had somthing to do with it being used brass. So I grabbed a new starline case and seated a rifle primer. And I got the same results as befor, perfect seating. Now I'm using only starling brass so I don't know if other brass will fit a rifle primer. Another thing I'm wondering is do I gain anything from being able to use large rifle primers.