MBZ Complete Upper Assembly

Photos are for illustration. The upper you receive may differ slightly in color or small parts.

The MBZ Complete Upper Assembly turns your AR-15 into a multi-caliber rifle. Drop it on your lower, pick your first barrel below, and change caliber later by swapping the barrel, not the upper. Choose your first MBZ Barrel Kit (required) and your color. Order more barrel kits later: every MBZ Barrel Kit fits every MBZ upper. Other Cerakote colors are available on request. Contact us before you order.

What's in the box

• MBZ threaded upper receiver with Picatinny rail, your first barrel mounted with its MBZ Barrel Adapter
• Aluminum handguard
• Side-charging bolt carrier group
• Spanner wrench

Built in Evansville, Wisconsin

• Billet 7075 aluminum upper receiver, anodized and finished in Cerakote Black, FDE or OD Green
• Aluminum handguard that unscrews for the barrel swap and threads back to a stop, so it returns to its original position. Accessories mounted on the handguard come off first, because of the gas tube.
• Fits a standard mil-spec AR-15 lower receiver

Swapping the barrel

Take any accessories off the handguard, unscrew the handguard, loosen the Adapter with the spanner wrench and pull the bolt back slightly to unlock the barrel. Slide the new barrel in, release the bolt, snug the Adapter with the wrench and give it a light tap, then screw the handguard back on. No torque wrench, no gunsmith. Your optic stays on the receiver. 6.5 Grendel and 6mm ARC barrels need their own bolt assembly, and 7.62x39 needs its own as well.

Shipping

An upper assembly is not a firearm under federal law and ships directly to you. Some states and localities restrict certain parts or barrel lengths: check your local law before you order. See our Shipping & Returns page.