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 experimented with a slight modification to an existing bolt carrier with regards to ergonomics for slick side uppers, the project had turned into a fun project with practical and reliability improvements.
The S in SBCG stands for Secure Staking, 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
https://www.m4carbine.net/showthread.php?195130-On-loose-carrier-key-screws
Some argue that as long as the gas key screws are torqued to spec and staked properly, OCKS aren't necessary. While that's true, for us, it is a matter of over building in areas where providing another layer of fail safe and redundancy is worth the negligible cost. Given the numbers below, the choice of OCKS is an easy one to make.
Install torque spec is 50-58 in-lb
Removal torque spec is 55-100 in-lb
Testing consistently found removal torque of YFS screws averaging around 76 in-lb, with the OCKS consistently at 132 in-lb.
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. SBCG will ship as is, having been slightly lubed and dirtied by the test firing procedure.
Serrated or dimpled surface is machined in the concave area (forward of the gas vents of the carrier) to facilitate silent bolt closing on upper receivers without a forward assist.
SBCG carriers have a small Cygnus laser engraved. SBCGs are distinctive looking in their own right (form follows function, we didn't go out of our way to make them look different), the subdued logo fits our narrative and practice of modest to secret logo placement. It's an identifier, not an advertising device.
* SBCG bolts are manufactured from properly and correctly heat treated AISI 9310 steel. Each Bolt is MPI tested and inspected. Each bolt is shot peened and comes with a Sprinco heavy extractor spring and black O ring. The bolt and cam pin have been NP3 treated to enhance corrosion resistance and carbon build up.
* Bolt is stress relieved.
* Sprinco 5-Coil Heavy Duty Extractor Spring
* Black Insert
* MPI tested
* SBCG carriers are ASSI 8620 steel and 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 (NP3) 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.
RE: NP3 coating, we've been asked to coat SBCGs in nitride or NIB. While our pre-production SBCGs (all 40 of them) were NiB coated, there will not be a production SBCG with NIB.
NP3 has a coefficient of friction as low as .07-.1 according to test standards LFW-1 and ASTM D-2714. Nickel Boron has a coefficient of friction as low as .08-.2. NP3 has PTFE also known as Teflon® co-deposited in the nickel matrix. As wear occurs, new PTFE particles are exposed and the self lubricating properties continue. Nickel boron has a surface with many high points. Because the high points make all the contact, there is less surface area for friction to occur. The problem with this is once the high points wear down the coefficient of friction increases due to more surface area being contacted. With no self lubricating particles like Teflon® in the Nickel Boron matrix, there is no additional lubrication after the contact points are worn. The bottom line is that if you see wear on Nickel Boron, it has lost its “Self Lubricating” properties at that spot.
NOTE:
* 2019 and later production SBCGs no longer has NP3 coated extractors.
* SOTAR cam pin is standard from December, 2019 production. For more info on the SOTAR cam pin, please visit this page: https://www.forwardcontrolsdesign.com/SCP-SOTAR-Cam-Pin_p_206.html
* The time it takes to assemble, QC, testing (including test firing) SBCGs means we simply don't have time to do that many of them a year, SBCGs will be a constrained item as long as we uphold the standards we impose on them, we have no plans to relax our QC standards.
