There are generic power piston that will work. I don't have the material to tell which one they are. I load for 12, 20, & 28 gauge shotguns. I load for heavy shot loads in all gauges, unless I am at the trap and Sheet range. I used an 1-3/8oz load in my 12gauge and only changed the shot size, depending on what I was after. The steel shot kind of took me out of duck hunting. I have several barrel for the 870 I used in 12 gauge, from 24" I.P. Choke to a 34" trap barrel. I set my boys with same system. If the birds especially dove were flying high I would move my 34" barrel, and reach out there. Some places I hunted around people using and thinking there 7/8 or 1oz loads were anti aircraft guns, and are sky busters. with the 1-3/8oz loads I could easy reach 50yds on most birds. With the 34" I could reach somewhere around 80+yds on dove. You should have watch them trying to reach out there wondering why I was taking my birds and they weren't.
Back to reloading. Look at several manuals to see what does work. Graf & Son and Ballistic Products have a fair amount of info and charts. I used deep cup piston to hold the shot in them. The deeper the cup the tighter the shot column out to longer distances. The heaver shot loads, the denser the pattern is for longer ranges. Shot sizes also extends ranges too. I have several P/W presses. They make a pressure that you can get the plates from 410 2 1/2 to 10 gauge 3 1/2 gauge, and all the stops in between.
The only thing is primers: The reloading manuals call out the primer for each manufactures hull. I don't know it they are inter chainable. Now I have cross Fed 209 into Winchester, Federal cases and a few others, with on problem. I don't recommend others doing that. I feel that the overall shots shell primers may vary in length some, and that were the problem maybe at. The internal length of base height is what you have to watch for.
