10.5″ .300 Blackout AR-15 Upper – Suppressor Ready with 15″ M-LOK Handguard
Build the ultimate suppressed .300 Blackout AR pistol or SBR with this 10.5″ .300 Blackout AR-15 upper, engineered for reliability, durability, and outstanding suppressed performance. Designed around a tucked suppressor configuration, this upper features a 15″ free float M-LOK handguard with a generous 1.7″ inner diameter, allowing many suppressors to fit partially inside the rail for a sleek, integrated appearance. Includes a fake can to use as well if you’re waiting on yours to get approved.
The .300 AAC Blackout cartridge was developed specifically to deliver excellent performance from short barrels, making a 10.5″ upper an outstanding choice for home defense, range use, hunting, and suppressed shooting. Whether you’re shooting lightweight supersonic loads or heavy subsonic ammunition, this upper is built to perform.
Key Features
10.5″ .300 Blackout Barrel
- 10.5″ barrel length
- .300 AAC Blackout
- 1:8 twist
- 4150 CMV steel
- Nitride finish
- Pistol-length gas system
- 5/8×24 muzzle threads
Suppressor-Ready 15″ M-LOK Handguard
- Large 1.7″ inside diameter
- Designed for tucked suppressor builds
- M-LOK accessory slots
- Continuous Picatinny top rail
- Anti-rotation tabs for a secure fit
Mock Suppressor Included
Every upper ships with a removable mock suppressor installed, giving your build the finished tucked appearance until you’re ready to install your suppressor.
Mil-Spec Upper Receiver
- Forged 7075-T6 aluminum
- Type III hardcoat anodized
- M4 feed ramps
- Dust cover installed
- Forward assist installed
Gas System
- Steel low-profile gas block
- Stainless pistol-length gas tube
Muzzle Device
- A2-style flash hider
- Standard 5/8×24 threads
Built Right – Ready to Run
Every Mid State Firearms upper is assembled by experienced builders using quality, in-spec components.
Optional Test Fire
Add one of our bolt carrier groups and we’ll test fire your upper with that exact BCG before it ships, ensuring it’s ready to install on your lower receiver.
Why Choose a 10.5″ .300 Blackout Upper?
The 10.5″ .300 Blackout upper has become one of the most popular AR-15 configurations because the cartridge was designed to perform exceptionally well from short barrels.
Benefits include:
- Excellent suppressed performance
- Reliable cycling with subsonic and supersonic ammunition
- More efficient powder burn than 5.56 in short barrels
- Compact overall length
- Ideal for home defense, hunting, range use, and truck guns
- Outstanding suppressor host
If your goal is building a compact suppressed AR, it’s difficult to beat a 10.5″ .300 Blackout upper.
Technical Specifications
- Caliber: .300 AAC Blackout
- Barrel Length: 10.5″
- Twist Rate: 1:8
- Barrel Material: 4150 CMV Steel
- Finish: Nitride
- Gas System: Pistol Length
- Thread Pitch: 5/8×24
- Handguard Length: 15″
- Handguard ID: 1.7″
- Receiver: Forged 7075-T6
- Receiver Finish: Type III Hardcoat Anodized
- Gas Block: Low Profile Steel
- Gas Tube: Stainless Steel
- Muzzle Device: A2 Flash Hider
- Assembly: Professionally Assembled
Important Legal Information
- This is an upper receiver assembly only and is not a serialized firearm.
- Installing this upper on a lower receiver may create a firearm regulated under the National Firearms Act depending on the lower receiver and overall configuration.
- It is the purchaser’s responsibility to comply with all applicable federal, state, and local laws.
- Commonly used with AR pistol lowers or lawfully registered short-barreled rifles (SBRs).
Perfect For
- Suppressed .300 Blackout builds
- AR pistol configurations
- Registered SBRs
- Home defense
- Hunting
- Compact truck guns
- Tactical and range rifles
Why Choose a 10.5″ .300 Blackout Upper?
| Barrel | Advantages | Best For |
|---|---|---|
| 8–9″ | Maximum compactness, optimized for subsonic suppression | Dedicated suppressed builds |
| 👉 10.5″ (This Upper) | Excellent balance of velocity, reliability, and suppression | All-around .300 Blackout build |
| 16″ | Higher velocity with supersonic loads | Hunting and general-purpose rifles |
A 10.5″ .300 Blackout upper offers one of the best all-around barrel lengths for the caliber. It provides excellent performance with both subsonic and supersonic ammunition while maintaining the compact handling characteristics that make .300 Blackout such a popular choice.
Choose Mid State Firearms as your trusted build supplier.
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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.