URF-B v3 is incompatible with ADM's ambi lower, its oversized upper paddle is too large for the URF-B's bolt catch cutout.
URF v3 is a follow on development of URF-B v2, and will replace URF-B, v2 as we ramp up production.
Functionally, v3 and v2 share the same features, even if v3 looks slightly different than v2.
URF v3 retained the following features:
* LMT MARS-L lower compatibility
* Compatibility with most MLOK and Picatinny handguards
* Beveled area in the upper rear section to allow easier folding backup sight access
* Hole above the gas tube hole for handguards that use a pin for anti-rotation.
Additional changes for URF v3:
* Beveled area for BUIS access is now on all three sides (left, right, and rear)
* Slightly wider receiver wall, this has the effect of forming a fence for the bolt catches
* Charging handle latch pocket changed to be closer to TDP spec (0.06) and tolerances while maintaining compatibility with 3rd party charging handles (many uppers have this pocket at 0.08, twice the TDP spec depth at 0.04, +0.000/0.02)
URF v3 are billet uppers machined from 7075, and Type III hard coat anodized.
Weight: 9.01oz.
Proudly designed and made in USA.
NOTE
URF-B v3 is incompatible with ADM's ambi lower, its oversized upper paddle is too large for the URF-B's bolt catch cutout.
Re: a tight fit between the upper and lower, this is an often asked question so we'll discuss it briefly. Tighter is better for some applications, a tight fitting upper and lower isn't one of them. URF v3's pivot pin and take down pin lugs are made according to TDP dimensions and specs, we don't make them oversized in order to create a tight fit with any lower receiver, since it doesn't do a thing for accuracy and reliability.
