The USR™ Upper Standard Receiver is a precision machined upper with a special proprietary bore that is ultra smooth 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.
Material: Billet 7075-T6 Aluminum
Finish: Milspec Type3, Class2 Deep Black Hardcoat Anodize.
Super smooth Bore.
M4 Feedramps as standard.
Made in the USA.
Stripped Weight 7.0oz (197g).