The Stern Defense MAG-ADMP9&40/P320 converts your standard mil-spec AR-15, M4, or M16 lower assembly to accept S&W M&P, P320, and P250 magazines in 9mm and .40 S&W. Made in the U.S.A. and constructed from 6061 T6 aircraft grade aluminum with hard coat anodized type 3 finish, this adapter delivers precision-engineered performance for serious shooters.
The MAG-ADMP9&40/P320 installs in seconds with no permanent modifications, and features true last-round hold open—a critical advancement that elevates both functionality and reliability. The ergonomic mag release ensures smooth operation across extended shooting sessions, while compatibility with all generations of M&P magazines and any mil-spec AR-15 lower receiver provides maximum versatility for customized builds.
This adapter is ideal for law enforcement professionals, competitive shooters, and civilian AR enthusiasts looking to consolidate their magazine systems. The adapter requires the use of a 9mm or .40 S&W barrel (depending on chosen caliber) and a Glock-cut bolt. Built with precision and backed by Stern Defense’s reputation for quality, the MAG-ADMP9&40/P320 enables seamless caliber transitions while maintaining mil-spec reliability standards.
