Compact Power. Suppressor-Ready Performance.
The 10.5″ .300 AAC Blackout AR-15 Upper from Midstate Firearms is built for shooters who want maximum performance in a compact platform. Featuring a pistol-length gas system, this upper is optimized for reliable function with both subsonic and supersonic .300 BLK ammo, making it ideal for suppressed or unsuppressed use.
Whether you’re building a home defense rifle, truck gun, or compact range setup, this upper delivers consistent cycling, solid accuracy, and hard-hitting performance.
Key Features
- 10.5″ .300 AAC Blackout Barrel
- 1:8 twist rate (stabilizes subs & supers)
- Pistol-length gas system for reliable cycling
- .750 gas block journal
- Dimpled for gas block (180° from gas port)
- 5/8×24 threads (suppressor-ready)
- 10″ Lightweight Free Float M-LOK Handguard
- Slim profile for weight reduction and handling
- Full M-LOK compatibility for accessories
- Mil-Spec Upper Receiver
- 7075-T6 forged aluminum
- Type III hardcoat anodized black
- M4 feed ramps for improved reliability
- Gas System Components
- Low-profile steel gas block
- Stainless steel gas tube
- Included Components
- A2 flash hider
- Forward assist
- Dust cover
- Built Right
- Professionally assembled by experienced builders
- QC checked for alignment, torque, and function
Why Choose a 10.5″ .300 Blackout Upper?
.300 Blackout is designed to perform in short barrels, making 10.5″ one of the most efficient and versatile configurations available:
- Excellent performance in compact platforms
- Superior suppressor compatibility
- Reduced flash and concussion vs 5.56
- Reliable cycling with subsonic ammunition
Perfect for AR pistols, SBR builds, and suppressed setups.
Optional BCG – Test Fired for Reliability
Select a bolt carrier group and we’ll test fire your upper with that exact BCG before it ships.
No tuning. No guesswork. Just a ready-to-run upper out of the box.
Shop Quality BCGs from Mid State Firearms
Ideal Use Cases
- Home defense
- Suppressed shooting
- Truck / backpack gun
- Range use
- Hunting (short to mid-range)
Technical Specifications
- Caliber: .300 AAC Blackout
- Barrel Length: 10.5″
- Twist Rate: 1:8
- Gas System: Pistol Length
- Gas Block Diameter: .750
- Thread Pitch: 5/8×24
- Handguard: 10″ Free Float M-LOK
- Receiver: 7075-T6 Forged
- Finish: Type III Hardcoat Anodized
- Muzzle Device: A2 Flash Hider
-300x300.png "15' Gen1 Free Float Quad Rail, photo")
sound of freedom – This was a great set up. I loved being able to customize the set up. Only issue I had was my own fault as a newb to building these. I used a heavy barrel in a slim hand guard. It makes adding attachments tough with clearances. Hoping someday to also get an AR10 from here.