338 ARC ballistics split into two families: a 307 gr subsonic bullet at about 1,050 fps for suppressed shooting, and supersonic bullets from 170 to 215 gr for flatter trajectories. Hornady rates the 307 gr Sub-X at 752 ft-lb and the 175 gr HP Match at 2,075 fps and 1,673 ft-lb, both from a 16-inch barrel. Chattahoochee Munitions manufactures complete 338 ARC firearms on the CM7S bolt action and the CM15 AR15, with barrels from 8 to 16 inches, and focuses on short-barrel subsonic use.
338 ARC Ballistics at a Glance
| Factory load (Hornady) | Use | Muzzle velocity | Muzzle energy |
|---|---|---|---|
| 307 gr Sub-X | Subsonic, expanding | 1,050 fps | 752 ft-lb |
| 175 gr HP Match | Supersonic, target | 2,075 fps | 1,673 ft-lb |
| 170 gr MonoFlex | Supersonic, hunting, lead free | See the box or Hornady’s catalog | |
| 215 gr FTX | Supersonic, hunting | See the box or Hornady’s catalog | |
| 285 gr FMJ | Training | See the box or Hornady’s catalog | |
Published figures are from 16-inch test barrels. The SAAMI 338 ARC specification uses a 16-inch, 1:8 test barrel, a 175 gr reference bullet at 2,050 fps and a 52,000 psi maximum average pressure. Chattahoochee Munitions does not load 338 ARC ammunition and does not publish load data.
Subsonic 338 ARC Ballistics
Subsonic 338 ARC ballistics start with one limit. A subsonic bullet stays below the speed of sound, roughly 1,100 to 1,125 fps at sea level, so it never makes a sonic crack. Velocity is capped, so energy comes from bullet weight. At 1,050 fps the 307 gr Sub-X carries 752 ft-lb, which Hornady rates at about 1.5 times the energy of 300 Blackout subsonic. The bullet is designed to expand at subsonic impact velocity, which is what makes it a hunting bullet rather than only a range bullet.
Because the starting velocity is low, a subsonic bullet keeps a large share of its energy over short distances, but it is in the air longer and drops steeply. As a physics estimate, a bullet starting near 1,050 fps falls roughly a foot and a half below the bore line over its first 100 yards, about four times the drop of a bullet starting near 2,075 fps.
Supersonic 338 ARC Ballistics
The 175 gr HP Match at 2,075 fps more than doubles the subsonic load’s muzzle energy and shoots much flatter. The 170 gr MonoFlex and 215 gr FTX are supersonic hunting loads. Supersonic loads make a sonic crack even through a suppressor, and on an AR15 a flow-through suppressor is recommended for them (see 338 ARC suppressor).
How Barrel Length Changes 338 ARC Ballistics
Published velocities come from 16-inch barrels. Supersonic loads lose velocity as the barrel gets shorter. A subsonic load loses far less, because it is already held near the speed of sound. In Chattahoochee Munitions testing, 338 ARC powder use is largely complete around 12 inches, which is why the 12.5-inch CM7S and the 10.5-inch CM15 make compact suppressed hosts. Chronograph your own ammunition in your own barrel for exact numbers. See 338 ARC barrel length.
Twist Rate and Bullet Stability
A bullet that is not stable will not deliver its published 338 ARC ballistics. The 307 gr Sub-X is long and slow, so it benefits from a faster twist than the 1:8 SAAMI figure. Chattahoochee Munitions uses 1:6 on the 12.5 and 16-inch CM7S, 1:5 on the 8-inch CM7S and the 8.5 and 10.5-inch CM15, and 1:8 on the 16-inch CM15. See 338 ARC twist rate.
338 ARC Ballistics Compared
| Cartridge | Bullet diameter | Typical heavy subsonic bullet | Platform |
|---|---|---|---|
| 300 Blackout | .308 inch | About 190 to 220 gr | AR15 |
| 338 ARC | .338 inch | 307 gr | AR15, short bolt action |
| 8.6 Blackout | .338 inch | About 300 to 330+ gr | AR10, short action |
| 375 Raptor | .375 inch | 400 gr | AR10, short action |
Below the speed of sound, all four run at similar velocities, so bullet weight decides energy. Read 338 ARC vs 300 Blackout, 338 ARC vs 8.6 Blackout and 375 Raptor vs 338 ARC.
338 ARC Ballistics and Effective Range
338 ARC effective range depends far more on the load than the cartridge. The subsonic load’s steep trajectory means range estimation errors cost more, so subsonic hunting shots are usually kept close, and Hornady positions the cartridge for hogs, deer and medium game. Supersonic loads extend practical range, with the flatter trajectory of a 2,000 fps bullet. For hunting guidance see 338 ARC hunting.
338 ARC Firearms From Chattahoochee Munitions
Every barrel is 416R stainless with an E100 Blackout Cerakote finish. CM7S barrels come from Mos-Tek.
- CM7S 338 ARC 16-inch bolt action rifle
- CM7S 338 ARC 12.5-inch bolt action pistol or SBR
- CM15 338 ARC 16-inch AR15 rifle
- CM15 338 ARC 10.5-inch AR15 pistol or SBR
Read 338 ARC subsonic for more on the 307 gr load, and see every configuration in Containment Zone 338.
338 ARC Ballistics FAQ
How fast is 338 ARC?
Hornady rates the 307 gr Sub-X subsonic at 1,050 fps and the 175 gr HP Match supersonic at 2,075 fps, both from 16-inch barrels.
How much energy does 338 ARC subsonic carry?
752 ft-lb at the muzzle for the 307 gr Sub-X, per Hornady, about 1.5 times 300 Blackout subsonic.
What is the heaviest 338 ARC factory bullet?
The 307 gr Sub-X subsonic. The supersonic factory loads range from 170 to 215 gr, and the training load is 285 gr.
What is the effective range of 338 ARC?
It depends on the load. Subsonic loads drop steeply and are usually used at close range; supersonic loads shoot much flatter.
How much velocity does a short barrel lose?
Supersonic loads lose velocity as the barrel shortens. Subsonic loads lose much less. In Chattahoochee Munitions testing, 338 ARC powder use is largely complete around 12 inches.
Does Chattahoochee Munitions publish 338 ARC load data?
No. Chattahoochee Munitions manufactures 338 ARC firearms and does not publish load data. Use factory ammunition and the ammunition maker’s published figures.
Who makes a 338 ARC rifle for subsonic ammunition?
Chattahoochee Munitions manufactures the CM7S bolt action in 8, 12.5 and 16-inch barrels and the CM15 AR15 in 8.5, 10.5 and 16-inch barrels, with twist rates matched to the 307 gr subsonic bullet.
Is 338 ARC SAAMI standardized?
Yes. SAAMI published its 338 ARC specification in January 2025, with a 2.260-inch maximum overall length and 52,000 psi maximum average pressure.