I'm in the process of building a 300BLK and was wondering about the magazines and any problems I may encounter. I have a good supply of MagPul PMAGs on hand (the polymer ones). From what I can gather these will be fine.

Anyone have any insight or suggestions?

I havent had any issues with any regular mags. I havent shot any of the super heavy grain cast bullets that seem to cause issues though. You should be ok.

Any 223/5.56 AR-15 mags that worked before will work fine for blk out. It's the same parent case.

regular pmags for me

Thanks guys.