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// Kit · Carrier completion kit
Carrier Completion Kit — Nitride Cam Pin
Three small parts, and the two that get lost. One of them now tells you which way it went in.
The sensible buy
$25.00
- SKU KIT-SOT-CCK-NIT
- Contents Three parts
- Cam pin Black nitride
- Mark SOT arrowhead
- Fits AR-15 / M16 5.56 BCG
Questions about fit? Tell us the rifle and the barrel and we’ll confirm the right part before it ships.
// The operator’s case
The firing pin retaining pin is the part that lives on the workshop floor.
Anybody who has stripped an AR at a bench, in a truck or in poor light knows the sequence: the retaining pin comes out, goes somewhere, and is never seen again. The cam pin is not much better — it is small, it is dark, and it goes back in whichever way it happened to be facing. And the firing pin, when it breaks, stops the rifle completely.
This kit is those three parts together: a chrome plated firing pin machined to the mil-spec print from 8740 steel, a retaining pin, and a black nitride cam pin. Buying them as a set costs less than buying them one at a time and means the drawer has a complete set rather than two thirds of one.
The cam pin is where this kit differs from every other completion kit on the shelf. Ours carries the SOT arrowhead with SOT inside it, laser marked on the head, and the rule is one line long: the arrow point faces toward the bolt face.
What this kit will not do
It will not make a rifle more accurate, more reliable or faster to cycle. Three correct parts do what three correct parts do. What changes is that one mistake — putting the cam pin back the wrong way round — becomes a five-second check on a part you are already holding.
A rule on the part beats a habit in the owner.
// Why it
A rule on the part beats a habit in the owner.
01 The cam pin states a direction
A cam pin beds in. The surfaces carrying load develop a wear pattern that matches the way the pin has been sitting, so turning it around presents unbedded surfaces to loads they have not seen — and passes the wear into the bolt, which is the part that breaks. An arrowhead is a rule anyone can apply to a pin they have never seen before, rather than a witness mark that only says “back the way it was last time”. The case for indexing is Chad Albrecht’s, taught at the School of the American Rifle armourer’s course; the arrowhead is what we added.
02 The retaining pin you will lose
It is the cheapest part in the rifle and the one most likely to vanish during a strip. Having a spare in the kit is the difference between finishing a clean and hunting a carpet with a torch.
03 A firing pin to the mil-spec print
8740 steel, precision ground, properly heat treated and chrome plated. Protrusion is what decides whether primers are struck properly — too little gives light strikes, too much risks slam fires — so being made to the print matters more here than on most parts.
04 Black nitride cam pin
Nitride is a surface conversion rather than a plating — it grows into the steel instead of sitting on it, so there is no coating to chip at an edge. It is hard, slick and corrosion resistant, and it matches a nitride or phosphate carrier group rather than standing out bright inside one.
05 Cheaper as a set
Bought individually these three parts cost more than $25.00, and you will usually be paying shipping twice. The kit exists because these are the parts people need together and rarely buy together.
06 It is what our own groups use
The same three parts, to the same specification, that go into the bolt carrier groups we build — including the marked cam pin. Offering the kit separately means you do not have to buy a group to get them.
// Specifications
The specification
| Specification | Value |
|---|---|
| Product | Carrier Completion Kit — Firing Pin, Retaining Pin, Nitride Cam Pin |
| SOT SKU | KIT-SOT-CCK-NIT |
| Contents | Firing pin · firing pin retaining pin · cam pin |
| Firing pin | 8740 steel, machined to the mil-spec print, precision ground, properly heat treated, chrome plated |
| Retaining pin | Firing pin retaining pin (cotter type) |
| Cam pin | Black nitride, carrying the SOT arrow index mark — arrow point faces toward the bolt face |
| Fits | AR-15 / M16 5.56 bolt carrier groups |
| Price | $25.00 |
// Before you order
Installation and inspection.
- Install the cam pin with the arrow point facing toward the bolt face, and check it every time the bolt is stripped. It needs no tools.
- Check the firing pin tip, not just the shank — that is the end you cannot see with the bolt assembled.
- Fit the retaining pin fully. A partially seated retaining pin can walk out under cycling.
- These parts are for 5.56 AR-15 / M16 bolt carrier groups. They are not the .308 / AR-10 parts.
- Components, not a firearm. Function check the bolt carrier group before firing.
WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
Warranty. Supplied unmodified and carrying their manufacturer’s warranty in full. The SOT mark is applied to the cam pin head and does not alter any load-bearing dimension. Second of Ten will act as the owner’s agent in any claim against that coverage where it runs broader than ours. See warranty information.
// Related
Related parts and groups
All bolt carrier group parts and the comparison → Bolt Carrier Groups →
Bombproof by Design™ and Gundaddy® are marks of Second of Ten LLC. School of the American Rifle and SOTAR are the property of their respective owners and are referenced here to credit the origin of the cam pin indexing practice; this product is not affiliated with, endorsed by or produced in conjunction with the School of the American Rifle. Specifications are subject to change without notice. Firearm components should be installed and function checked by a qualified armourer before firing.
Bombproof by Design™
Precision // Purpose // Performance