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 or dimples 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.
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 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.
Sprinco 5-Coil Heavy Duty Extractor Spring
100% HPT & MPISBCG carriers are machined to USGI specifications. The M16/M4 carrier includes a mil-spec gas key. The gas key is heat treated per TDP specifications and NP3 coated. The gas key is secured to the carrier via OCKS (Optimized Carrier Key Screws), torqued to spec values, and properly staked.
Each carrier assembly is treated with a durable Nickel/PTFE plating which creates a permanently lubricious surface which reduces the need for lubrication.
Note that we do advocate proper lubrication between any two moving parts. NP3 coating notwithstanding, it is advised to apply lubrication on key areas of the carrier, bolt, and charging handle, and inside the upper receiver.