6mm ARC, By the Numbers
6mm ARC was designed by Hornady in response to a U.S. Department of Defense request for a lightweight AR-15 cartridge that could hit man-sized targets at distances a 5.56 cannot reach. Hornady built it on the 6.5 Grendel case necked down to 6 mm with the shoulder moved back .030″, so long, high-BC bullets seat within the AR-15’s 2.260″ magazine length, specified a 1:7.5 twist to stabilize them, and standardized it with SAAMI at 52,000 psi for gas guns. Faxon was among the first barrel makers to chamber it.
Hornady’s own comparison: substantially better ballistics than 5.56 with less drop and less wind deflection, comparable performance to 6.5 Grendel from a wider assortment of bullets, and .308-class reach with substantially less recoil in a package 30 to 35 percent lighter. The 108 gr ELD Match leaves a 24″ barrel at 2,750 fps and is still doing 1,971 fps with 931 ft-lb at 500 yards.
The 20″ MATCH-X Target sits between Hornady’s 24″ test barrel and the 16 to 18″ carbines most people build, giving up roughly 75 to 100 fps to the published figures while keeping the rifle balanced and the rifle-length gas system’s soft impulse. Hornady develops its gas-gun load data in an 18″ 1:7.5 barrel.
Hornady factory data — 6mm ARC 108 gr ELD Match, 24″ test barrel
| Range | Velocity | Energy | Drop (200 yd zero) |
| Muzzle | 2,750 fps | 1,813 ft-lb | — |
| 100 yd | 2,582 | 1,599 | +1.9″ |
| 200 yd | 2,421 | 1,405 | 0 |
| 300 yd | 2,265 | 1,230 | −7.8″ |
| 400 yd | 2,115 | 1,072 | −22.4″ |
| 500 yd | 1,971 | 931 | −44.8″ |
Source: Hornady published ballistics from a 24″ test barrel. The 103 gr ELD-X Precision Hunter is rated 2,800 fps and 1,793 ft-lb from the same length. Expect roughly 75–100 fps less from the 20″ MATCH-X Target.
What You Need to Build It
6.5 Grendel-pattern bolt (.136″ bolt face) and Grendel magazines; carrier, upper, buffer, and barrel nut are standard AR-15. .750″ gas block and a rifle-length gas tube. Headspaced with a 6mm ARC go/no-go gauge.
What Every MATCH-X Barrel Shares
416-R stainless bar stock, drilled, reamed to 32 Ra, honed to 8 Ra before the rifling button goes through, 5R button rifled, stress relieved at 1150°F, contoured, chambered, then lapped back to a uniform 16 Ra from throat to crown. Bore and groove air-gauged at three points, honed finish read on a profilometer, borescoped, chamber verified on a CMM, magnetic-particle inspected, nickel-Teflon extension torqued to 150 ft-lb, pinned, and headspaced. Exterior left as bare stainless blasted with S110 media. Made in Greater Cincinnati, Ohio, backed by the Faxon Lifetime Guarantee. See the whole MATCH-X line and the process video ›
MATCH-X 6mm ARC FAQs
What bolt and magazines does 6mm ARC use?
A 6.5 Grendel-pattern bolt with a .136″ bolt face and 6.5 Grendel magazines. A 5.56 bolt will not headspace. Everything else is standard AR-15.
Why 1:7.5?
It is the twist Hornady designed the cartridge around and the one in the SAAMI spec. The 103 to 108 gr bullets that give 6mm ARC its reach need it; lighter 58 to 90 gr loads shoot fine through it.
How does 6mm ARC compare to 6.5 Grendel and 22 ARC?
All three share the Grendel bolt and magazines. 6mm ARC has the widest bullet selection and the best balance of BC and recoil; 22 ARC is faster and flatter with .224 bullets; 6.5 Grendel carries the heaviest bullets. Pick by the bullet you want to shoot.
Do I need an adjustable gas block?
It is worth having. Loads range from 58 gr varmint to 108 gr match, suppressor use is common, and the ammunition is loaded to a 52,000 psi gas-gun ceiling. The Faxon .750″ adjustable block meters the port to your load.
