We ran a small batch of NiB, UCT coated BCGs, these are the precursors to the SBCG, the final versions of which may contain several variants with different coating and bolts. Most of the features of the SBCG have been incorporated in the pre-production units, save for the use of OCKS (Optimized Carrier Key Screws), and some pre-production SBCG may have cosmetic blemishes (they do not affect functionality, most are next to impossible to discern), thus these units are marked as blemished and sold at a reduced cost.
What started out as a slight modification to an existing Wiley Arms bolt carrier design with regards to ergonomics for slick side uppers and uppers without a forward assist, had turned into a fun project with practical and reliability improvements.
It is our view that the factory M16 carriers are very good, and improvements over them would be hard to come by. Modern coatings have made them easy to clean and quite slick, which we can appreciate.
We're not into sacrificing reliability for the sake of light weight, and we view cosmetic changes as anything but fashion that have no place on a combat/duty/defense rifle.
The S in SBCG stands for Secure Stacking, Slick Side. SBCG carrier has a series of serrations to aid in closing an out of battery bolt on upper receivers without a forward assist. The carrier still has forward assist pawl notches, and so is compatible with forward assist equipped uppers. **Please note that pre-production SBCG has standard gas key screws.**
The Secure Staking aspect involves SBCG's use of Ned Christiansen's OCKS (Optimized Carrier Key Screws), which when staked properly, offer significant improvement over conventional screws. OCKS have sharp, deep and effective knurling that extends to the top of the screw head. These splines form pockets for carrier key metal to flow into when the key is staked, resulting in gear tooth like engagement. Please go to this page for additional info and discussion http://www.m4carbine.net/showthread.php?195130-On-loose-carrier-key-screws
We use Permatex to provide a good seal between SBCG's gas key and carrier.
Since we're so keen on the gas key's staking to ensure its immobility, the question of one piece carrier had come up. It is our opinion that something different isn't always something better. Gas keys can crack, and be dropped and damaged, debris or primer can find its way into the gas key. Our view is based on reality, not a theory, as all of these have happened. A conventional carrier with a separate gas key can simply have its gas key replaced, which is impossible for any one piece carrier.
Each pre-production SBCG has its firing pin protrusion checked, gas key torqued and staked, and is individually test fired (5rds of XM193) by our able partners at Sionics Weapons System. SBCG will ship as is, having been slightly lubed and dirtied by the test firing procedure.
Full auto style carrier, NiB UCT treated. *** Note that it is our belief that the user should always apply lubrication between reciprocating surfaces, NiB UCT or not ***
Case hardened 8620 aircraft quality steel
Gas Key: 4130 with Grade 8 hardware properly staked into a milled slot for proper positioning
Cam pin: hardened 4340 steel
Firing pin 8740 steel and hard chrome coated
Serrated surface in the concave area to facilitate silent bolt closing on upper receivers without a forward assist
Fits M4/AR15 syle rifles. 223/5.56mm, 300BLK
Carpenter 158 Steel
Shot peened, NiB coated with UCT EXO process
Extractor 4340 Steel-Mil-Spec Spring & O-Ring combination
Magnetic Particle Inspected, and HPT tested