Mag-AD9 adapter converts a mil-spec AR-15 lower to accept S&W M&P and Sig P320/P250 9mm and .40 S&W magazines. Machined from 6061-T6 aluminum with Type III hard coat anodize and a 4140 NiB-coated feed ramp.
The Stern Defense Mag-AD9 magazine adapter converts a mil-spec AR-15 lower into a platform that accepts S&W M&P and Sig P320/P250 magazines in 9mm and .40 S&W. It is machined from 6061-T6 aircraft-grade aluminum and finished with a Type III hard coat anodize. The unit includes a 4140 NiB-coated feed ramp and a last-round hold-open feature for straightforward magazine handling.
Product Specifications
The adapter accepts S&W M&P and Sig P320/P250 magazines in 9mm and .40 S&W.
The body is constructed from 6061 T6 aircraft grade aluminum.
The feed ramp is finished in 4140 NiB coating.
The exterior finish is Type 3 hard coat anodized.
The unit requires a Glock-cut bolt to function as specified.
The adapter provides a last-round hold-open feature for positive magazine presentation.
The product requires use with a 5.4 ounce buffer or heavier when using a carbine spring, and the buffer is not included.
The adapter is intended for use with any mil-spec AR-15 lower receiver.
According to manufacturer information, all gun components besides the bolt and barrel remain stock.
The item is designated as an AR-15 accessory in the product data.
The adapter is made in the USA.
The product dimensions are listed as 3.45 x 4.40 x 8.65 inches.
The listed height is 3.4500 inches, width is 4.4000 inches, and length is 8.6500 inches.
The finish/color is described as 9MM MAGAZINE ADAPTER for a 5.56mm lower.
The UPC for this product is 850001176217.
The Mag-AD9 is a practical component for builders and shooters who want a reliable, factory-style interface between common 9mm/.40 S&W handgun magazines and a mil-spec AR-15 lower. It is suited for range training, caliber conversion projects, and other applications where magazine commonality and low-cost ammunition are priorities. The adapter’s machined aluminum construction and hardened feed ramp are intended to provide durable, repeatable magazine alignment and feeding behavior in a converted lower.
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