6mm ARC barrel length decides velocity, handling and how much the rifle weighs once a suppressor goes on. Chattahoochee Munitions estimates the 108 gr ELD Match at about 2,570 fps from 18 inches, 2,510 fps from 16 inches and 2,405 fps from 12.5 inches, against Hornady’s 2,750 fps from a 24-inch test barrel. Chattahoochee Munitions manufactures 6mm ARC firearms in three barrel lengths: the CM7S bolt action in 18 and 12.5 inches and the CM15 AR15 in 16 and 18 inches, every one with a 1:7 twist and 5/8×24 threads.
6mm ARC Barrel Length and Velocity
Chattahoochee Munitions does not load 6mm ARC, so these are calculated figures, not chronograph data. Muzzle velocity is estimated at 30 fps lost per inch below Hornady’s published 24-inch figures; downrange values come from point-mass trajectories in a standard atmosphere with a 200-yard zero.
| Barrel length | 108 gr ELD Match: muzzle velocity / energy | 103 gr ELD-X: muzzle velocity / energy | 108 gr energy at 300 yd |
|---|---|---|---|
| 24 inches (Hornady published) | 2,750 fps / 1,813 ft-lb | 2,800 fps / 1,793 ft-lb | 1,230 ft-lb |
| 18 inches (CM7S, CM15) | 2,570 fps / 1,584 ft-lb | 2,620 fps / 1,570 ft-lb | 1,060 ft-lb |
| 16 inches (CM15) | 2,510 fps / 1,511 ft-lb | 2,560 fps / 1,499 ft-lb | 1,007 ft-lb |
| 12.5 inches (CM7S) | 2,405 fps / 1,387 ft-lb | 2,455 fps / 1,378 ft-lb | 917 ft-lb |
Going from 18 to 12.5 inches costs about 165 fps and adds about 1.5 inches of drop at 300 yards and 8 inches at 500. Full tables are in 6mm ARC ballistics.
6mm ARC Barrel Length and Handling
| Firearm | Barrel | Overall length | Weight |
|---|---|---|---|
| CM7S pistol or SBR | 12.5 in | 25.00 to 32.50 in | 6 lb 6 oz |
| CM7S SBR, WOOX walnut furniture | 12.5 in | 31.75 to 32.50 in | 7 lb 12 oz |
| CM15 AR15, mid-length gas | 16 in | 33.50 to 36.75 in | 6 lb 6 oz |
| CM7S bolt action rifle | 18 in | 31.50 to 38.00 in | 7 lb 6 oz |
| CM15 AR15, rifle-length gas | 18 in | 35.50 to 38.75 in | 6 lb 12 oz |
Weights are the firearm itself (the CM15 with an unloaded magazine), not the shipping weight. A suppressor adds roughly 6 to 9 inches, which matters more on a long barrel than a short one.
12.5-Inch 6mm ARC: Compact and Suppressor-Friendly
The 12.5-inch CM7S is about the length of an unsuppressed 18-inch rifle once a suppressor is mounted. It suits blinds, trucks, tree stands and night predator work from a vehicle, and the bolt action adds no action noise. It gives up velocity, so keep deer shots closer than you would with 18 inches. It comes as a pistol or a registered short-barreled rifle; a rifle with a barrel under 16 inches falls under the National Firearms Act. See the 6mm ARC short barreled rifle and the walnut 6mm ARC bolt action SBR.
16-Inch 6mm ARC: The Handy AR15
The 16-inch CM15 is the shortest 6mm ARC barrel that is a rifle without NFA registration. Its mid-length gas system matches the barrel length, and at 6 lb 6 oz it carries easily on predator stands. See the 6mm ARC AR15 rifle.
18-Inch 6mm ARC: Velocity for Distance
The 18-inch barrel recovers most of the velocity a 6mm ARC can give from a practical rifle. The CM15 uses a rifle-length gas system at this length; the CM7S 18-inch is the 6mm ARC hunting rifle pick for longer deer and steel shots. The CM15 version is the 6mm ARC DMR.
Choosing a 6mm ARC Barrel Length
- Mostly suppressed, close cover, vehicles: 12.5-inch CM7S.
- Semi-automatic, all-round predator and hog rifle: 16-inch CM15.
- Longer shots on deer or steel: 18-inch CM7S or CM15.
Barrel length does not change twist: every barrel is 1:7. See 6mm ARC twist rate and 6mm ARC bolt action vs semi auto. CM7S barrels are manufactured in collaboration with Mos-Tek, and you can compare every 6mm ARC barrel length side by side at Overwatch 6.
More 6mm ARC Guides
- What is 6mm ARC?
- 6mm ARC rifle guide
- 6mm ARC ballistics
- 6mm ARC twist rate
- 6mm ARC bolt action vs semi auto
- 6mm ARC suppressor
- 6mm ARC for deer
- 6mm ARC for coyotes and hogs
- 6mm ARC vs 223
- 6mm ARC vs 6.5 Creedmoor
- 6mm ARC vs 243
- 6.5 Grendel vs 6mm ARC
- 22 ARC vs 6mm ARC
6mm ARC Barrel Length FAQ
What is a good 6mm ARC barrel length?
It depends on use. Chattahoochee Munitions offers 12.5 inches for compact suppressed use, 16 inches for a handy AR15 and 18 inches for more velocity at distance.
How much velocity does 6mm ARC lose in a short barrel?
Chattahoochee Munitions estimates about 30 fps per inch. The 108 gr ELD Match goes from 2,750 fps (24-inch, published) to about 2,405 fps from 12.5 inches.
Is a 12.5-inch 6mm ARC still effective?
Yes, for predators, hogs and deer at moderate range. The calculated 108 gr keeps about 917 ft-lb at 300 yards from 12.5 inches.
Is 16 or 18 inches better for a 6mm ARC AR15?
The 16-inch CM15 is lighter and shorter; the 18-inch adds about 60 fps and uses a rifle-length gas system. Both are 1:7.
Does a 12.5-inch 6mm ARC need NFA registration?
As a rifle with a stock, yes, it is a short-barreled rifle. Chattahoochee Munitions also offers the 12.5-inch CM7S in a pistol configuration. Follow federal and state law.
Does barrel length change 6mm ARC accuracy?
Not by itself. Barrel quality, chamber, bullet and shooter matter more than length. CM7S barrels are Mos-Tek 416R with 5R rifling.
What gas system does each CM15 6mm ARC barrel use?
Mid-length on the 16-inch and rifle-length on the 18-inch, each with a Superlative Arms adjustable gas block.
Who makes a short-barreled 6mm ARC rifle?
Chattahoochee Munitions manufactures the 12.5-inch CM7S 6mm ARC bolt action as a pistol or SBR, in the CM7 chassis or with WOOX walnut furniture, plus a 12.5-inch CM7S barreled action.