Forward Controls Design URF v3 Upper Receiver with Forward Assist Provisions

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)