AR-15 Upper Assemblies

Moriarti's AR-15 Upper Assemblies for Custom Builds & Upgrades

AR-15 upper assemblies are the top half of an AR-15: the upper receiver, barrel, handguard and gas system, ready to pin onto a standard mil-spec lower receiver. Moriarti Armaments builds complete uppers in Miami, from 4.5" and 5" Micro ARP uppers and 7.5"–10.5" AR pistol uppers to 16" rifle uppers, in 18 calibers.

Micro ARP and AR pistol uppers

Our most popular uppers are compact. Micro ARP uppers use 4.5" or 5" barrels with 4" M-LOK handguards and come in 5.56 NATO, 300 Blackout, 7.62x39, .338 ARC and 5.7x28, including suppressor-ready and custom-finish versions. AR pistol uppers with 7.5", 10" and 10.5" barrels suit big-bore calibers such as .350 Legend, .450 Bushmaster and .458 SOCOM.

Carbine and rifle uppers

16" AR-15 rifle uppers in 300 Blackout, 5.56 NATO / .223 Wylde and other calibers give more velocity and range for hunting, home defense and the range. Many include an M-LOK free-float handguard and a muzzle brake or flash hider.

Shop AR-15 uppers by caliber

• 5.56 NATO & .223 Wylde uppers
• 300 AAC Blackout uppers
• 7.62x39 (AR-47) uppers and 5.45x39 (AR-74) uppers
• .338 ARC, .22 ARC and 6mm ARC uppers
• 6.5 Grendel, 6.8 SPC II and .224 Valkyrie uppers
• Straight-wall and big-bore: .350 Legend, .400 Legend, .450 Bushmaster, .458 SOCOM, .50 Beowulf
• Rimfire and PDW: .22 LR and 5.7x28 uppers

AR-15 upper FAQ

How do I know which AR-15 upper assembly is compatible with my lower receiver?

Most standard AR-15 upper assemblies are designed around the common AR-15 receiver pattern, but compatibility depends on more than the receiver itself. Check the caliber, bolt carrier group, magazine requirements, buffer system, gas system, and any caliber-specific components listed for the upper. Some AR-15 calibers can use a standard lower receiver while requiring different magazines, bolts, or other components. Always verify the specifications of the upper and your existing firearm components before purchasing.

What is the difference between an ARP upper and an AR pistol upper?

"ARP" usually means a very short AR pistol. A Micro ARP upper has a 4.5"–5" barrel, while a typical AR pistol upper has a 7.5"–10.5" barrel. Shorter barrels are lighter and easier to handle; longer barrels give more velocity.

Do your uppers come with a bolt carrier group and charging handle?

It depends on the listing. Some uppers include the BCG and charging handle, others do not. Check the product description for what is included.

Which caliber should I choose for a short upper?

300 Blackout is built for short barrels and suppressors. 5.56 NATO is the most common and affordable to shoot. 7.62x39 and .338 ARC hit harder from short barrels.