I have read Thermold magazines will not work in a Armalite, the most common reason offered has been Armalites are made to tight. I just received  my Thermold magazines from Bushmaster. At first bolt would only close half way so I called Bushmaster. Bushmaster explained to me sometimes there is a flashing on the mag ears from the molding process that needs to be filed off. I checked, and sure enough the molding flashings were there. I filed down the flashing on one magazine, on another I scraped the flashing off with the sharp blade of a multitool. The scraping method with the blade of the multitool worked best. The flashing sticks up only a RCH so you only have to go over the top of the mag ears a few times. I applied Son of A Gun Protectant by STP to the mags for lube and protection and the mags function properly and look great.They hold the bolt open and feed properly. Once you scrape the flashings off use the top flat side of the blade (Opposite cutting) and lightly burnish the plastic smooth.