With the weight of a loaded mag you really have to be careful of weight. I have mostly chicom and Eastern European mags that I bought in the 90’s that work really well. I recently bought some Bulgarian steel and polymer mags that work well except for the 5&10 round mags. The only 30 rd mags that haven’t worked for me are the $5 unity mags. They fall out, the rear lug needs filed or ground down some to work. I have not tried the pmags. Shooting prone and using the mag as a monopod works well no problem.