We think the standard A3 upper receiver is pretty good, and hard to improve on (cosmetics don't count), but there are couple of areas we always wished the manufacturer would change. It was one of these "why can't they make it like this, it'd be easier/better" that led to the URF.
URF is based on CMT's URPR-1 7075 billet upper receiver. Type 3 hard coated in black, it is an excellent basis for the two ergonomics driven changes we've always wanted:
1. Relief cuts on the section before rails start for better accessibility of a flip up BUIS's sight stalk / flip up element.
2. Relief on the top of forward assist housing. The relief cut is specifically designed for ambi charging handle users. When the user uses his right fingers to pinch and grasp the CH's right latch, the relief allows the index finger to reach down further, so the CH's right latch is positioned in the middle of his finger pad, not the tip of it, for a more secure purchase, especially if the user has gloves on. When we use our left fingers to grab the charging handle's left latch, there is nothing below the latch, but on an upper with forward assist, its housing stands in the way. The relief simply provides what room that can be spared on the FA housing so more of the user's finger can have a positive purchase.
The FA housing relief is a simple broad stroke. In retrospect, we could have made its presence less shockingly obvious. The change we made is there to work, we didn't give much thoughts to how it'd look, only that it'd create as much clearance as the FA housing can afford to give. Our design philosophy emphasizes utility, innovation and quality derived advantages, aesthetics is a super minority in this equation.
New for 2019, URF v2 features an over pressure relief vent below the shell deflector. The over pressure relief vent is drilled diagonally from below the shell deflector. When a round is fired, gas is routed through the gas tube, enters the carrier and impinges on the bolt and its gas rings. As the carrier and bolt travel rearward in recoil, gas is vented through the carrier’s gas ports, and continues to do so past the ejection port. At this point, since the carrier’s gas ports are now masked by the receiver, they vent gas into the upper receiver. Gas seeks a way out of the upper receiver, typically through the gap in the forward assist and forward assist housing, and in between the upper and charging handle. The over pressure relief vent provides a better (larger opening than the others) and more direct path, the path of least resistance, for the gas to be evacuated elsewhere.
The over pressure relief vent doesn't aim to redirect all gas to be vented through it, it does aim to decrease the volume and velocity of the exiting gas through all openings the pressurized gas will find. The relief vent is tapped and can be closed off by way of a set screw (1/8" Allen key is required) if the user doesn't shoot suppressed. The vent is located below the shell deflector.
URF v2's and URF-S v2's over pressure gas relief vent is licensed from BATTLEARMS IP under U.S. Patent No. 8,910,406
Also new in v2 is LMT MARS receiver compatibility. URF v2's shell deflector has been re-contoured to accommodate MARS receiver's right side bolt catch/release.
URF v2 is available with or without a forward assist.
* 5 axis machined from 7075 T6 billet
* M4 feed ramps
* Engraved “T” numbers
* Over pressure gas relief vent for suppressed use
* 1913 picatinny Rail flat top
* Mil Spec Type III class II hard coat anodized Black
* Shell deflector
* Forward Assist machined into receiver (on standard URF v2 only, URF-S v2 has no provisions for a forward assist)
* Dust cover port machined into receiver
* Increased wall thickness for added rigidity
* Compatible with Mil spec parts
* Compatible with most aftermarket handguard/rail systems
* Lifetime warranty against manufacture defects
* Anti-rotation hole above gas tube hole
* Compatible with "Tactical Link" Enhanced Battery Assist Lever
* Comes stripped without dust cover & forward assist assembly
* Weight: 8.9oz