Home / Parts / Bolt Carrier Group Parts / SOT Arrow Index Cam Pin
// Small parts · Cam pin
SOT Nitride Arrow Index Marked Cam Pin
The cheapest part in the bolt carrier group. And one of the few that can be installed wrong without telling you.
SOT arrow index
$20.00
- SKU CAM-SOT-NIT
- Finish Salt bath nitride
- Construction Mil-spec
- Mark SOT arrowhead
- Orientation Point toward bolt face
Questions about fit? Tell us the rifle and the barrel and we’ll confirm the right part before it ships.
// The operator’s case
Almost nobody thinks about the cam pin. It comes out during cleaning, and it goes back in whichever way it happened to be facing.
That is the problem, and we did not work it out on our own. Chad Albrecht of the School of the American Rifle teaches it in his armourer’s course, which is where Dr. Bennett learned it. A cam pin is not symmetrical in service: it beds in, and the surfaces that have been carrying load develop a wear pattern that matches the way the pin has been sitting. Turn it around and you present unbedded surfaces to loads they have not seen, and bedded surfaces to loads they were not carrying. The fit gets worse rather than better, and the wear the pin passes into the bolt increases — which matters, because bolts break and cam pins rarely do.
Installing the pin the same way every time is free. The only thing standing in the way is that a bare cam pin gives you nothing to reference. 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.
Note what that gives you over a plain witness mark. A witness mark only tells you the pin is back the way it was last time, which is useful but relies on it having gone in correctly on day one. An arrow states a direction — so a pin that has passed through three owners and two armourers can still be checked against a rule rather than against its own history.
What this part does not do
It does not make the bolt carrier group stronger, faster or smoother. It is a standard mil-spec cam pin with a mark on the head. The whole value is that a mistake which was previously invisible becomes a five-second check — and that the check works on a pin you have never handled before.
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 A direction, not just a witness
The mark is an arrowhead, and it points. That makes it a rule anyone can apply on a pin they have never seen before: point toward the bolt face. A dimple or a scribe tells you only that this pin is oriented as it was the last time somebody put it in — which is worth having, but is only as good as whoever did it first. We would rather the part carry the instruction than the owner carry the memory.
02 It reads out of the rifle
The reference is the bolt face — a feature of the part the pin goes into, not of the rifle. So the check holds with the bolt out of the carrier and the carrier out of the upper, which is exactly the moment the pin is in your hand and exactly when the mistake gets made.
03 Salt bath nitride
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 off an edge. Hard, slick, corrosion resistant, and it will not flake into a fire control group.
04 Mil-spec construction
Standard dimensions, standard material. This is not an oversized or proprietary part — it drops into any mil-spec AR-15 / M4 bolt carrier group in place of the pin that came with it.
05 Marked on the head, not the body
The mark sits on the head, where you can see it with the pin installed and the carrier open. Nothing is engraved on a bearing surface, so nothing about the mark changes how the pin carries load.
06 Where the idea comes from
The case for indexing a cam pin is Chad Albrecht’s, taught at the School of the American Rifle armourer’s course. We are repeating an argument we were taught, not one we invented, and we would rather say so. What we added is the arrowhead, so the mark carries a direction rather than only a memory.
07 It is on our own builds
The SOT arrow mark is on the cam pin in every SOT Enhanced bolt carrier group we sell. On a standard bolt that is a mil-spec pin like this one; on an HMB™ bolt it is the radiused HMB™ pin, a different part made for the HMB™ socket. This pin is offered on its own because a customer with a good standard carrier group already does not need to buy another one to get the mark.
// Specifications
The specification
| Specification | Value |
|---|---|
| Product | SOT Nitride Arrow Index Marked Cam Pin |
| SOT SKU | CAM-SOT-NIT |
| Construction | Mil-spec |
| Finish | Salt bath nitride |
| Mark | SOT arrowhead with SOT inside it, on the pin head |
| Installed orientation | The arrow point faces toward the bolt face |
| Compatibility | Mil-spec AR-15 / M4 bolt carrier groups |
| Also supplied in | The same SOT arrow mark is on the cam pin in every SOT Enhanced bolt carrier group and the SOT Enhanced Chrome Bolt. HMB™ bolts and groups carry it on the radiused HMB™ cam pin, which is a different part |
| Price | $20.00 |
// Before you order
Installation.
- Install with the arrow point facing toward the bolt face.
- Check the orientation every time the bolt is stripped for cleaning. It takes a glance and needs no tools.
- A cam pin that has been running in one orientation has bedded in that orientation. If you find one reversed, it is not a safety fault — correct it and carry on.
- This is a component, not a firearm. Where SOT fits it, it goes in correctly and is checked as part of the build.
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.
// 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. This is a firearm component and should be installed by a qualified armourer; the bolt carrier group should be function checked before firing.
Bombproof by Design™
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