Lantac's USR Upper Standard Receiver is a precision machined upper with a special proprietary bore, creating an ultra smooth surface with a roughness average in micro inches of 16, as opposed to standard bored or milled uppers that are 32-63, or higher.

This reduces bolt carrier friction and creates a much smoother operation. Barrel nut threads, bore and barrel extension surfaces are all machined in one operation so that they are perfectly concentric and perpendicular to the barrel and fixing assembly.

Features:

• Machined from Billet 7075-T6 Aluminum
• Finished with a Milspec Type 3, Class 2 Deep Black Hardcoat Anodize
• Exceptionally Smooth Bore
• M4 Feed Rams