SKU: 100039215
UPC: 850001176040
MPN: 001SDMAGADMP45A
This Stern Defense, Llc adapter converts a standard mil-spec AR-15, M4, or M16 lower into a platform that runs Smith & Wesson M&P .45 ACP pistol magazines. It drops into the magazine well and installs in seconds, making it a straightforward route for shooters building an AR-pattern pistol-caliber carbine or pistol chambered in .45 ACP. It works with every generation of M&P .45 magazine, so anyone already carrying a Smith & Wesson .45 sidearm can share magazines between handgun and carbine. The adapter targets law enforcement users and civilian builders who want commonality across their .45 ACP kit.
The body is machined from 6061 T6 aircraft-grade aluminum with a hard coat type 3 anodized finish, paired with a 4140 NiB-coated feedramp for smooth feeding and corrosion resistance. A last round hold open feature locks the bolt back on an empty magazine, which standard blowback PCC builds often lack. The adapter also includes an ergonomic magazine release for fast reloads. Running .45 ACP through an AR lower requires the right supporting parts: a .45 ACP barrel, a Glock-cut bolt, and an upper with an enlarged ejection port to clear the larger case. Many builders pair the adapter with a heavier buffer for reliable cycling. The unit is made in the USA.
Use this adapter when you want a .45 ACP carbine or pistol that feeds from magazines you already own, cutting cost and simplifying logistics at the range or in a patrol bag. It suits home-defense builds, training guns, and suppressed setups where subsonic .45 ACP shines. Confirm your barrel, bolt, and upper meet the requirements above before assembly. If you are sourcing the rest of the build, check our rifle parts and AR-15 buffer selection, and stock up on ammunition for break-in and load testing.
It accepts all generations of Smith & Wesson M&P .45 ACP pistol magazines. The adapter installs into a standard mil-spec AR-15, M4, or M16 magazine well, letting you share .45 ACP magazines between a compatible Smith & Wesson handgun and your AR-pattern carbine or pistol.
Beyond the adapter you need a .45 ACP barrel, a Glock-cut bolt, and an upper receiver with an enlarged ejection port to clear the larger case. Many builders also use a heavier buffer to tune cycling for reliable feeding and ejection with .45 ACP loads.
Yes. The adapter includes a last round hold open feature that locks the bolt to the rear on an empty magazine. That capability is uncommon on standard blowback pistol-caliber carbine builds and speeds up reloads and chamber checks.
The body is machined from 6061 T6 aircraft-grade aluminum with a hard coat type 3 anodized finish. The feedramp is 4140 steel with a NiB coating for smooth feeding and corrosion resistance. It is made in the USA per manufacturer specifications.
Installation takes seconds. The adapter drops into the magazine well of a compatible mil-spec lower, so swapping between standard rifle magazines and the .45 ACP setup is quick once your barrel, bolt, and upper meet the build requirements.
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