Moriarti AR-10mm 10.5" Slick Side Premium Complete Upper Receiver, LRBHO

AR-10mm 10.5" Upper: Specs

The AR-10MM 10.5" Slick Side Premium Upper by Moriarti Arms is built for precision, performance, and rugged use in compact platforms. Featuring a Last Round Bolt Hold Open (LRBHO) function and a blowback operating system, this upper is ideal for those building a reliable and high-performance 10mm AR pistol or SBR setup.

The 10.5” match-grade barrel is crafted from 4150 chrome moly steel, finished with a durable black nitride coating. Chambered in 10MM Auto, it has a 1:16 twist and 9/16x24 threads, finished with a standard A2 flash hider. The billet slick side upper receiver is precision machined from certified 7075-T6 aluminum and black hardcoat anodized to military specs.

This complete upper also includes a slim, rifle-length M-LOK free-float rail, ideal for customization and enhanced barrel cooling. The included .40 S&W/10mm BCG is Glock and Colt style compatible, machined from US-made 8620 steel, and phosphate coated for durability.

Upper Features:

• Barrel: 10.5” 10MM Match Grade, 4150 CrMo Steel, Black Nitride Finish

• Twist Rate: 1:16

• Thread Pitch: 9/16x24 with A2 Flash Hider

• Gas System: Blowback

• Receiver: Billet 7075-T6 Aluminum, Slick Side Design, Black Hardcoat Anodized

• Handguard: 10" Lightweight Free-Float Rifle-Length M-LOK Rail

• Bolt Carrier Group: AR-40 .40 S&W/10MM, US-Made 8620 Steel, Phosphate Finish, Glock/Colt Compatible

• Charging Handle: Mil-Spec AR-15

• Compatibility: Works with Glock-style AR-45 lowers and standard AR-15 components

• LRBHO Feature: Last Round Bolt Hold Open

• Assembly: Fully Assembled and Tested

• Made in the USA by Moriarti Armaments

Note: This upper is part of Moriarti’s premium line. Product images may vary slightly due to design updates.

FAQ

What lower does it fit?

A dedicated pistol-caliber AR lower that takes Glock-style 10mm magazines. A standard AR-15 lower with 5.56 magazines will not feed it.

How does it operate?

It is a direct blowback pistol-caliber design with no gas tube or gas block, so a heavy PCC buffer is used for reliable cycling.

Does it have last round bolt hold open?

Yes. It has LRBHO, so the bolt locks back after the last round when used with an LRBHO-compatible lower.

Is a lower receiver included?

No. This is an upper assembly only; the lower receiver and magazine are sold separately.

Related: AR-10mm upper assemblies · pistol caliber carbines

Images may not be an exact representation of the product.