Alexander Arms UST17 17 HMR Complete Upper Assembly - 18" Black Cerakote Aluminum Receiver with M-LOK Handguard for AR-15, Includes 2 Magazines

The Alexander Arms UST17 17 HMR complete upper assembly brings specialized rimfire power to your AR-15 platform. Built on a dedicated 17 HMR upper receiver, this precision-engineered system swaps onto a standard AR-15 lower, letting you add a dedicated varmint and small-game upper to your existing rifle without replacing the whole gun. The 18-inch straight-flute barrel is optimized for the 17 HMR cartridge with a 1:9 twist rate and sports a 1/2-28 RH threaded muzzle capped with an A2 flash hider.

This upper runs a blowback operating system — no bolt carrier group or charging handle swap needed — and features a LAR Alexander Arms-branded M-LOK handguard finished in black anodized aluminum. The upper assembly itself weighs 4.5 pounds, keeping your rifle nimble for long days in the field. Two 10-round magazines come included, giving you ready-to-shoot capacity out of the box.

Whether you're serious about prairie dog control, hunting ground squirrels, or just want a tack-driving rimfire platform with AR ergonomics, this 17 HMR upper delivers accuracy and reliability in a modular package. The 17 HMR's flat trajectory and minimal recoil make it ideal for precision shooting at distance, and the dedicated upper means you're not compromising the setup of a centerfire rifle to get there.

Key Features

• 18-inch straight-flute barrel optimized for 17 HMR performance
• 1:9 twist rate for stable bullet flight
• 1/2-28 RH threaded muzzle with A2 flash hider
• Blowback operating system — no BCG changes required
• LAR Alexander Arms M-LOK handguard for modern mounting flexibility
• Black anodized aluminum receiver finish
• Two 10-round magazines included
• 4.5-pound upper weight for agile handling

Specifications

Frequently Asked Questions

Will this upper work on my AR-15 lower receiver?

Yes. This is a dedicated upper assembly that attaches to any standard AR-15 lower receiver. You'll use the same lower pin set and buffer system as any other upper.

What does 17 HMR ammo cost compared to other rimfire cartridges?

We don't have pricing data on ammunition, but the 17 HMR is a premium rimfire cartridge. Your best bet is to check current ammo availability and pricing at retailers before committing to the upper.

What's included in the box?

The complete upper assembly, two 10-round magazines, and a standard charging handle. You'll need to supply your own AR-15 lower receiver, bolt carrier group, and buffer system.

Can I add a suppressor or other muzzle device to this upper?

The barrel is threaded 1/2-28 RH, which is standard for 17 HMR and many rimfire accessories. Any suppressor or brake rated for 17 HMR and 1/2-28 threading will work, but verify compatibility with your chosen device before purchase.