Tested the 30 round aluminum 5.56/.223/.300 BLK in all my lowers. Empty, they dropped completely free as I expected they should after comparing them to my Pmag Gen 2 and 3, and Hexmag. The stainless steel 20 round .350 Legend Duramags were already a known good fit for that rifle. Hadn't handled a metal 30-round since the military in 1997.I really like the Duramag magazines and they work where my Pmags don’t work reliably all the time. I think you will be happy with them and last where the Pmags I have to check for cracks all the time.