Home / Parts / Bolt Carrier Groups / YM 6mm ARC Chrome BCG
// Young Manufacturing · Complete bolt carrier group
YM 6mm ARC Chrome BCG w/ HMB™
Made in-house since 1991. And deliberately not staked — which deserves an explanation, not a footnote.
Sold as supplied
$299.95
- SKU BCG-YM-6ARC-CHR-HMB
- Chambering 6mm ARC
- Bolt HMB™
- Finish Hard chrome
- Gas key Torqued, not staked
Questions about fit? Tell us the rifle and the barrel and we’ll confirm the right part before it ships.
// The operator’s case
Young Manufacturing have been making bolt carriers since 1991, and they will not stake a gas key. That is not an oversight. It is a position, and it is worth understanding before you choose.
Start with what the group is. Young machine their carriers in-house on CNC from mil-spec quality steel, then heat treat, hard chrome, and chrome line the bolt throat. Sharp edges and rough finishes are taken off deliberately — their phrase is that it will not shred fingers. It is built to standard mil-spec design using the same steel and the same processes as their National Match line, and it carries their recoil-lug supported gas key.
On the carrier itself they add 30% more contact area on the upper and lower guide surfaces than a standard carrier, which aligns the carrier more precisely in the receiver. On their National Match bolt, three critical areas are precision ground after heat treatment — the rear of the bolt lugs, the centre support ring and the bolt tail — for consistent lockup shot to shot. This group is the standard model, built to the same processes.
The bolt is the HMB™, licensed from HM Defense: the pass-through cam pin hole becomes a socket, run with a radiused cam pin, so material is retained at the cam pin location rather than drilled away. It also reduces contact between cam pin and firing pin, and the socket holds lubricant where a through-hole cannot.
Where this sits in our range
We sell bolt carrier groups with hand-staked gas keys, and we index-mark the keys on our own Enhanced groups. We do neither to this one. It is sold exactly as Young Manufacturing build it, unmarked and unmodified — because their reasoning is honest engineering rather than cost-cutting, and a customer who has read their argument and agrees with it should be able to buy the product from us as they intended it.
We would rather stock both answers and explain them than pretend there is only one.
// Why it
Two answers to the same failure. Both worth understanding.
01 Why Young will not stake the gas key
Their argument, in their own president’s words, runs like this. Staking does not seal a gas key — it only stops the screws backing out. If the screws are not torqued correctly first, staking simply locks in a screw that is already loose or already over-torqued and prone to breaking; they report seeing plenty of staked screws that were one or the other. The mil-spec assembly drawing also calls for the gas key face to be sealed, which they observe almost nobody actually does. So instead of staking they degrease the key, the carrier face and the screw threads, apply a high-strength thread locker gel to the key face and the threads, and torque the screws to 56 inch-pounds. Young will not warranty a carrier with a staked key, regardless of who staked it.
02 Where Second of Ten stands on that
We index-mark gas keys on our own Enhanced groups precisely because a screw that backs out is the failure we want a customer to see coming. Young are attacking the same failure from the other end: get the torque and the sealant right and the screw should not move in the first place. Both positions agree on the thing that actually matters — a correctly torqued screw. They disagree about what to do afterwards. We think their reasoning is sound, we stock their product, and we would rather set the argument out than pretend it is not there.
03 30% more guide contact
Increased contact area on the upper and lower guide surfaces aligns the carrier more precisely in the receiver. It is a machining decision rather than a coating or a material claim, which makes it one of the more checkable things a carrier maker can say.
04 Hard chromed after heat treatment
The order matters. Chroming a fully hardened carrier puts the finish on a part that is already at final hardness, and the bolt throat is chrome lined separately — the surface the bolt actually rides in gets its own treatment.
05 The HMB™ bolt, retained not added
Cam pin socket in place of the pass-through hole, with a radiused cam pin. Note the wording: material is retained where a through-hole removes it. Nothing is bulked up and nothing is oversized, and it runs in a standard carrier.
06 Same processes as National Match
Young state this group is built from the same steel and by the same processes as their National Match line, to standard mil-spec design. What you are not paying for is the additional precision grinding that defines the NM bolt.
07 A 6mm ARC bolt face is not a 5.56 bolt face
This group is 6mm ARC, whose case head is derived from 6.5 Grendel and is larger than the mil-spec .378 face. The same bolt face is shared by 6.5 Grendel and .264 LBC. It is not interchangeable with 5.56, 6mm MAX, .300 BLK or .350 Legend, nor with 6.8 SPC or .224 Valkyrie. Fitting the wrong bolt is a headspace and safety problem, not an inconvenience.
// Specifications
The specification
| Specification | Value |
|---|---|
| Product | YM 6mm ARC Chrome BCG w/ HMB™ |
| Manufacturer item number | 1-50-12-015 |
| SOT SKU | BCG-YM-6ARC-CHR-HMB |
| Chambering | 6mm ARC |
| Bolt face | 6.5 Grendel derived |
| Also runs | Any cartridge on the 6.5 Grendel Type II bolt face — 6.5 Grendel and .264 LBC. Bolt face is necessary but not sufficient — see the note below |
| Carrier | Mil-spec quality steel, CNC machined in-house, heat treated, hard chromed. M16 profile. 30% more guide contact area |
| Bolt throat | Chrome lined |
| Bolt | HMB™ by HM Defense — cam pin socket in place of a pass-through hole, radiused cam pin |
| Gas key | Recoil-lug supported. Torqued to 56 in-lb with thread locker, deliberately not staked |
| SOT marks | None — this group is sold exactly as Young Manufacturing build it. We do not apply our arrow-index cam pin or index-marked gas key to it |
| Finish | Hard chrome, applied after heat treatment |
| Price | $299.95 |
// Before you order
Before you order — do not stake this gas key.
- Young Manufacturing will not warranty a carrier with a staked key, no matter who staked it, and will charge for a new key and for any labour needed to remove broken screws. If you want a staked gas key, buy a group built that way from the outset — several are on our shelf. If you want this group, run it as Young built it.
- Their further guidance if a key is ever removed: do not reuse the old screws. Fit new 10-32 x ¼ socket head cap screws, and if screws are to be staked at all, use a screw-type swaging tool rather than a hammer and punch, which can stretch the screw thread.
A shared bolt face is not the whole story. A cartridge sharing this bolt face means the bolt will hold the case head. It does not by itself mean the rifle will run. The barrel must be chambered for the cartridge, the magazine must feed it, and the gas system must be sized for it — and some of the cartridges listed need their own magazines rather than STANAG. Young Manufacturing do not publish a compatibility list for this group; the cartridges above are stated by Second of Ten on the basis of bolt face geometry. Tell us what you are building and we will confirm the whole system rather than just the bolt.
About this specification. The published listing for this item gives the part number, price and availability only. The manufacturing description above is Young Manufacturing’s published account of how they build their chrome bolt carrier groups, taken from their 5.56 listing and their own technical pages.
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 Young Manufacturing’s warranty in full — which expressly excludes any carrier with a staked gas key. Second of Ten will act as the owner’s agent in any claim against that coverage where it runs broader than ours, and warrants its own fitting and gauging work. See warranty information.
// Related
Related parts and groups
All bolt carrier groups and the comparison → Bolt Carrier Group Parts →
Bombproof by Design™ and Gundaddy® are marks of Second of Ten LLC. HMB™ is a mark of HM Defense, LLC. Young Manufacturing is a mark of Young Manufacturing, Inc. Marks are used for identification of components only, without implying endorsement or affiliation. The staking position described on this sheet is Young Manufacturing’s, summarised from their published technical page; it is reproduced here so the purchaser can weigh it, and does not constitute advice from Second of Ten. Specifications are as published by the manufacturer and were verified on 18 AUG 2026; they are subject to change without notice. Any bolt carrier group should be inspected and the rifle headspaced by a qualified armourer before firing.
Bombproof by Design™
Precision // Purpose // Performance