i was about to order some 5.56 mags listening to somebody else. from what i've been reading the 5.56 mags MAY work sometimes. i'm not willing to find out. i just ordered me some pmags for 300 blk. the ammo seems to be about the same price as 5.56.that was my problem. I got mad when holcomb shut down the IN economy March 2020 and bought the first AR I saw....a 300 bo.