I cannot answer your question about the Polish mags, but are used AK 74 mags in mine and they worked fine as long as I loaded 25 rounds or less. I never had an issue. Sometimes I would get a jam if I loaded 30 rounds. As I said in another reply to a similar question, there should be a tutorial available online on how to trim the followers to make them feed reliably. I’m pretty sure that a distributor of Romanian Sar threes was actually shipping AK 74 magazines with this modification along with new production rifles.