Alexander Arms UST17 Upper 17HMR 18″ Fluted Barrel

The Alexander Arms UST17 upper is supplied as a purpose-built AR-15 upper assembly offered in a 17-caliber rimfire configuration with an 18-inch fluted barrel. It ships with an M-LOK aluminum handguard, A2 flash hider, and a conversion kit that includes a recoil cassette, magazine well insert, and magazine catch to fit standard AR-15 lowers. The package also includes two 10-round magazines and is intended for precision rimfire practice and small-game/varmint applications.

Key Specifications

• The model is listed as Alexander Arms UST17 Upper.
• The barrel measures 18 inches.
• The barrel material is specified as steel.
• The upper includes a fluted barrel and A2 flash hider.
• The muzzle is threaded 1/2-28 RH.
• The handguard is a M-LOK aluminum handguard.
• The package includes two 10-round magazines and a .17 conversion kit.
• The assembly is listed to fit standard AR-15 lowers.
• The action type listed in supplier notes is blowback.

This upper provides a purpose-driven rimfire AR option with an 18-inch fluted barrel and modular M-LOK interface for accessories. With the included conversion parts and magazines, it delivers a ready-to-configure upper suitable for dedicated rimfire training, precision rimfire work, and varmint applications where a lightweight, low-recoil option is preferred.