338 Federal vs 8.6 Blackout compares two .338-caliber cartridges designed for opposite jobs. The 338 Federal is a supersonic hunting cartridge that fires 180 to 210 gr bullets at about 2,600 to 2,750 fps. The 8.6 Blackout is designed around heavy 300 to 352 gr subsonic bullets at about 1,000 fps for suppressed shooting, and it can also fire lighter supersonic loads. Chattahoochee Munitions manufactures both, and if quiet is the goal, the 8.6 Blackout is the one to choose.
338 Federal vs 8.6 Blackout Specifications
| Specification | 338 Federal | 8.6 Blackout |
|---|---|---|
| Bullet diameter | .338 inch | .338 inch |
| Parent case | 308 Winchester, necked up | Derived from the 6.5 Creedmoor case, ultimately the 308 Winchester family |
| Primary use | Supersonic hunting | Heavy subsonic, suppressed |
| Typical bullets | 180 to 210 gr | 300 to 352 gr subsonic; about 200 gr supersonic |
| Chattahoochee Munitions twist | 1:10 (CM10) | 1:3 for heavy subsonic or 1:5 (CM7S and CM10) |
| Chattahoochee Munitions barrel lengths | 18 inches (CM10) | 8, 12.5 and 16 inches (CM7S and CM10) |
| Recommended suppressor | Flow-through, rated for .338 | Enclosed on the CM7S and with subsonic ammunition on the CM10 |
Both cartridges are standardized by SAAMI.
338 Federal vs 8.6 Blackout Ballistics
Published figures: Federal lists the 338 Federal 185 gr Barnes Triple-Shock X at 2,750 fps and the 210 gr Nosler Partition at 2,630 fps from 24-inch barrels. Just Cause USA lists its 8.6 Blackout 350 gr Maker REX subsonic at 980 fps from a 12-inch barrel and 1,040 fps from 16 inches, and SAAMI’s 8.6 Blackout supersonic reference is a 200 gr bullet at 2,200 fps from a 16-inch barrel. Energy is calculated from weight and velocity. Chattahoochee Munitions does not load either cartridge.
| Load | Barrel | Velocity | Muzzle energy |
|---|---|---|---|
| 338 Federal 210 gr Partition | 24-inch test | 2,630 fps | 3,226 ft-lb |
| 338 Federal 185 gr Triple-Shock X | 24-inch test | 2,750 fps | 3,107 ft-lb |
| 8.6 Blackout 200 gr supersonic (SAAMI reference) | 16-inch | 2,200 fps | about 2,150 ft-lb |
| 8.6 Blackout 350 gr subsonic | 16-inch | 1,040 fps | about 840 ft-lb |
| 8.6 Blackout 350 gr subsonic | 12-inch | 980 fps | about 745 ft-lb |
Why the 338 Federal Is Not a Subsonic Cartridge
Subsonic loads have to keep velocity below the speed of sound, about 1,116 fps at sea level on a mild day. At that speed, the only way to add energy is bullet weight, and heavy .338 bullets are long. Long bullets need a fast twist to stay stable at low velocity. The CM10 338 Federal’s 1:10 twist is right for 180 to 210 gr bullets at 2,600 fps and above, but it cannot stabilize a 300 gr or heavier bullet at 1,000 fps. The 8.6 Blackout’s 1:3 twist exists for exactly that job. That is why Chattahoochee Munitions treats the 338 Federal as supersonic only. See 8.6 Blackout subsonic.
338 Federal vs 8.6 Blackout for Hunting
- Elk and moose at normal hunting ranges: 338 Federal. Its velocity and energy carry farther.
- Hogs and deer at close range, suppressed: 8.6 Blackout subsonic, usually inside 100 to 150 yards.
- Black bear: both are described as suitable with well-constructed bullets and good shot placement.
- Grizzly and brown bear: Chattahoochee Munitions points hunters to 458 SOCOM XL.
338 Federal vs 8.6 Blackout With a Suppressor
A suppressor on a supersonic 338 Federal reduces muzzle blast but leaves the bullet’s crack, and on the gas-operated CM10 Chattahoochee Munitions recommends a flow-through suppressor rated for .338. An 8.6 Blackout with subsonic ammunition and an enclosed suppressor removes the crack. On the CM7S bolt action there is no action noise either. Protect your hearing in every case; NIOSH publishes guidance on impulse noise.
338 Federal vs 8.6 Blackout: Which Firearm?
- 338 Federal: the CM10 338 Federal AR10, 18-inch 416R stainless 1:10 barrel, 7 lb 14 oz, three Cerakote finishes. See What is 338 Federal.
- 8.6 Blackout: the CM7S bolt action and CM10 semi-automatic at 8, 12.5 and 16 inches, every barrel Mos-Tek 416R in E100 Blackout Cerakote with a 1:3 or 1:5 twist. See Area 8.6.
Also compare 338 ARC vs 8.6 Blackout and 338 Federal vs 308.
More Variant Valley Guides
- What is 6.5 Creedmoor?
- 6.5 Creedmoor ballistics
- 6.5 Creedmoor barrel length
- 6.5 Creedmoor twist rate
- 6.5 Creedmoor for hunting
- 7mm-08 vs 6.5 Creedmoor
- What is 7mm-08?
- 7mm-08 vs 308
- What is 338 Federal?
- 338 Federal vs 308
- What is 358 Winchester?
- 338 Federal vs 358 Winchester vs 7mm-08
- 308 Winchester cartridge family
- 308 vs 6.5 Creedmoor
- 6mm ARC vs 6.5 Creedmoor
- 6.5 Grendel vs 6.5 Creedmoor
338 Federal vs 8.6 Blackout FAQ
Do 338 Federal and 8.6 Blackout use the same bullet?
They share the .338-inch diameter, but 338 Federal uses 180 to 210 gr bullets for supersonic speed and 8.6 Blackout is designed around 300 to 352 gr bullets for subsonic speed.
Can 338 Federal shoot subsonic?
Chattahoochee Munitions treats 338 Federal as supersonic only. Its 1:10 twist cannot stabilize heavy subsonic bullets. Choose 8.6 Blackout for subsonic .338.
Which hits harder, 338 Federal or 8.6 Blackout?
338 Federal, at about 3,100 to 3,200 ft-lb at the muzzle against about 2,150 ft-lb for the SAAMI 8.6 Blackout supersonic reference and 700 to 840 ft-lb for 8.6 Blackout subsonic.
Can I swap 338 Federal and 8.6 Blackout barrels?
Never fire a cartridge in a chamber not made for it. Each needs its own barrel and chamber.
Who makes 338 Federal and 8.6 Blackout rifles?
Chattahoochee Munitions manufactures the CM10 338 Federal AR10 and 8.6 Blackout firearms on the CM7S bolt action and CM10 semi-automatic platforms.