You can do what ever the hell you want, but you asked for help, and that's what your getting. Yes p mags should work but there are some rifles that don't like them, SS has one, mine and others have no issues. There's no milspec with large frame AR's tolerances very from each manufacturer, dpms should be good right out the box, I know mine was. Good luck, read a lot there's a ton of good info in here to absorb