What is 338 Federal? It is a .338-caliber, rimless, bottlenecked rifle cartridge made by necking the 308 Winchester case up to hold a .338-inch bullet. Federal introduced it in 2006, working with Sako, to put 180 to 210 gr bullets into a short-action rifle. It hits harder than a 308 with heavier bullets while staying in a 308-size action and magazine. Chattahoochee Munitions manufactures 338 Federal rifles on its CM10 large-frame semi-automatic platform with an 18-inch 416R stainless barrel and a 1:10 twist.
What Is 338 Federal at a Glance
| Specification | 338 Federal |
|---|---|
| Introduced | 2006, by Federal, with Sako |
| Parent case | 308 Winchester, necked up |
| Bullet diameter | .338 inch |
| Case length | 2.015 inches, the same as 308 Winchester |
| Maximum average pressure (SAAMI) | 62,000 psi |
| Common factory bullets | 180, 185, 200 and 210 gr |
| Published velocities (Federal) | 185 gr Barnes Triple-Shock X at 2,750 fps; 210 gr Nosler Partition at 2,630 fps |
| Chattahoochee Munitions twist | 1:10 on the CM10 338 Federal |
Cartridge and chamber dimensions are published in the ANSI/SAAMI centerfire rifle standard. Federal’s own account of the cartridge’s development is on Federal Premium.
What Is 338 Federal Used For?
Necking the 308 case up to .338 inch lets a short action fire much heavier bullets. A 210 gr .338 bullet has more frontal area and more mass than the 150 to 180 gr bullets common in 308 Winchester, which is why the 338 Federal is aimed at larger game in wooded and mixed country, where shots are usually inside 300 yards.
- Elk and moose: the cartridge’s main purpose, with 200 to 210 gr bonded or partitioned bullets.
- Black bear: suitable with a well-constructed bullet and good shot placement.
- Deer and hogs: suitable, especially in heavy cover where bullet weight helps.
For grizzly and brown bear, Chattahoochee Munitions points hunters to 458 SOCOM XL.
What Is 338 Federal Performance Like?
Muzzle figures in the first two rows are Federal’s published 24-inch numbers; energy is calculated from weight and velocity. The 18-inch rows are Chattahoochee Munitions estimates using an assumed loss of 30 fps per inch, not chronograph data. Chattahoochee Munitions does not load 338 Federal.
| Load | Muzzle velocity | Muzzle energy |
|---|---|---|
| 185 gr Barnes Triple-Shock X, 24-inch (published) | 2,750 fps | 3,107 ft-lb |
| 210 gr Nosler Partition, 24-inch (published) | 2,630 fps | 3,226 ft-lb |
| 185 gr, 18-inch CM10 (calculated) | 2,570 fps | 2,714 ft-lb |
| 210 gr, 18-inch CM10 (calculated) | 2,450 fps | 2,800 ft-lb |
For comparison, a 308 Winchester 178 gr ELD-X at Hornady’s published 2,600 fps carries about 2,672 ft-lb at the muzzle. See 338 Federal vs 308.
What Is 338 Federal Ammunition Like Today? Is It Discontinued?
No. 338 Federal remains a SAAMI-standardized cartridge, and Chattahoochee Munitions manufactures complete 338 Federal rifles today. Factory ammunition is made in smaller runs than 308 Winchester, so selection changes from season to season; check current catalogs and buy enough of one load to zero and hunt with.
Is 338 Federal a Subsonic Cartridge?
No. The CM10 338 Federal is a supersonic rifle with a 1:10 twist, which suits 180 to 210 gr bullets at full velocity, and Chattahoochee Munitions recommends a flow-through suppressor rated for .338 on it. If you want heavy .338 bullets at subsonic speed, that is the job of 8.6 Blackout, which uses a 1:3 or 1:5 twist for 300 gr and heavier subsonic bullets. See 338 Federal vs 8.6 Blackout, or 338 ARC subsonic for an AR15-size option.
338 Federal Compared With Other Cartridges
- 338 Federal vs 308: the same case, a larger bullet.
- 338 Federal vs 8.6 Blackout: supersonic .338 against subsonic .338.
- 338 Federal vs 358 Winchester vs 7mm-08: the three 308-family hunting cartridges.
Who Makes 338 Federal Rifles?
If you have asked what is 338 Federal good for in a semi-automatic, the answer is the CM10. The CM10 338 Federal uses an 18-inch 416R stainless barrel with 5R rifling and a 1:10 twist, rifle-length gas, a .750-inch Superlative Arms adjustable gas block, an adjustable buffer and 5/8×24 muzzle threads. It weighs 7 lb 14 oz with an unloaded magazine, measures 35 to 38.25 inches overall, and comes in Black Tungsten, Cobalt Kinetics Green or FDE Metallic Cerakote with one 10-round CM10 magazine. Browse CM10 338 Federal rifles or Variant Valley.
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
- 338 Federal vs 308
- 338 Federal vs 8.6 Blackout
- 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
What Is 338 Federal FAQ
Is 338 Federal based on the 308 Winchester?
Yes. It is the 308 Winchester case necked up to .338 inch, with the same case length and bolt face.
Who designed the 338 Federal?
Federal introduced it in 2006, developed with Sako.
Is 338 Federal good for elk?
Yes. Elk and moose are what it was designed for, with 200 to 210 gr bonded or partitioned bullets at normal hunting ranges.
Is 338 Federal good for bear?
Yes for black bear with a well-constructed bullet. For grizzly and brown bear, Chattahoochee Munitions points hunters to 458 SOCOM XL.
Is 338 Federal discontinued?
No. It is still a SAAMI-standardized cartridge and Chattahoochee Munitions manufactures 338 Federal rifles.
Will 338 Federal work in an AR10?
Yes. It shares the 308 bolt face and fits large-frame AR10 magazines. The CM10 338 Federal uses an 18-inch 1:10 barrel.
Who makes 338 Federal rifles?
Chattahoochee Munitions manufactures the CM10 338 Federal AR10 with an 18-inch 416R stainless 1:10 barrel, adjustable gas and an adjustable buffer, in Black Tungsten, Cobalt Kinetics Green or FDE Metallic Cerakote.
Who makes 338 Federal ammunition?
Federal introduced and loads it, and other makers have offered loads. Chattahoochee Munitions does not load 338 Federal ammunition.