Ati Mil Sport Complete Ar-15 - Upper 300 Aac 8.5" Black

The ATI Mil Sport Complete AR-15 Upper in .300 AAC is a ready-to-run upper receiver built for shooters who want short-range power in a compact package. The 8.5-inch barrel delivers the velocity and ballistics of .300 Blackout in a form factor that excels for close-quarters shooting, suppressed fire, and short-range hunting—without the unwieldy length of a full-size rifle. This is a complete upper assembly, so you get everything you need to bolt onto a compatible lower receiver and get to work.

The 7-inch M-LOK handguard gives you a modern, lightweight platform for mounting lights, lasers, foregrips, or other tactical accessories. M-LOK's modular slots are standard across the industry, so upgrades and customization fit without fuss. The polymer flip-up sights provide backup iron sights for rapid target acquisition—no batteries, no complicated zeroing, just simple, reliable aiming if your primary optic goes down.

ATI Outdoors built this upper to work as a complete unit; you're not cobbling together parts from different manufacturers or worrying about headspace and alignment. Whether you're building your first AR-15, rounding out a multi-caliber rifle collection, or assembling a capable truck gun or home-defense setup, this .300 Blackout upper handles the job with no compromises on quality or functionality.

Key Features

• .300 AAC Blackout caliber—subsonic-capable with excellent short-range stopping power
• 8.5-inch barrel for compact handling and faster target transitions
• 7-inch M-LOK handguard for easy accessory mounting
• Polymer flip-up sights included for reliable iron-sight backup
• Complete upper assembly—ready to mate to a compatible AR-15 lower receiver
• Black finish for a clean, professional appearance

Specifications

Frequently Asked Questions

What lower receiver does this upper work with?

This is a standard AR-15 complete upper assembly, so it will fit any AR-15 lower receiver that accepts a milspec upper. Confirm your lower is in proper working order and correctly assembled before mating it to this upper.

Can I use this upper for suppressed shooting?

.300 Blackout is purpose-built for suppressed fire, and this 8.5-inch barrel is well-suited to subsonic loads. Always verify that your suppressor and ammunition selection comply with your local laws and are appropriate for the .300 BLK cartridge.

What's included in the box?

You receive the complete upper assembly with the barrel, bolt carrier group, handguard, and polymer flip-up sights ready to install.

Is this a good choice for a short-range hunting or defensive rifle?

Yes. The .300 Blackout round, combined with the compact 8.5-inch barrel, makes this upper an effective choice for hunting medium game at close range and for home or property defense where shorter sight lines and faster handling matter.