u/Reader-xx

I have a smith & Wesson M&P 10 that I just inherited. I am working to educate myself on this platform. As part of the inheritance I received a bunch of PMag 20 plastic magazines. Regardless of which of them I use my rifle is jamming on about every 3rd round. One of the bullets jammed so bad the bullet end tilted at a 15% angle.

Is my problem likely to be the magazines or the gun itself? If its an easy fix like buying a different magazine id prefer to do that than to take it to a gunsmith.

Thanks for any advice