Welcome to the board. I'm guessing you have a Saiga 16" with a US buttstock, a 30rnd ProMag with a broken lip (feed ramp). You can install a bullet guide BG that will make the ProMag work again (if it was the lip). Search Dinzag.com here or google it.
You'll hear a lot of talk about converting the rifle to the standard AK pistol grip form or using hi cap mags. To do that you must have 5 US parts on the rifle (4 if you don't use a pistol grip). Most common are the magazine (3- body, follower, floorplate), fire control group FCG (3- hammer, disconnector, trigger), pistol grip, stock, f