300 Blackout vs 7.62×39 looks close on paper: two .30-caliber intermediate cartridges with similar supersonic energy. The difference is what each was designed for. The 7.62×39 is a supersonic military cartridge that needs its own bolt and magazines in an AR15. The 300 Blackout keeps the AR15’s 5.56 bolt and magazines and is designed to fire heavy bullets subsonic through a suppressor. Chattahoochee Munitions manufactures the CM15 300 Blackout AR15 in 5, 7.5, 10.5 and 16-inch barrels, the CM15-SD, 300 Blackout uppers, and the CM7S 300 Blackout bolt action in 8, 10 and 12.5 inches.
300 Blackout vs 7.62×39 at a Glance
| 300 Blackout | 7.62×39 | |
|---|---|---|
| Bullet diameter | .308 inch | .310 to .312 inch |
| Case | Shortened .223 Remington, 1.368 inch | Tapered, about 1.52 inch |
| Typical supersonic bullet | 110 to 150 gr | 120 to 125 gr |
| Subsonic loads | Designed for them, 190 to 245 gr | Few |
| AR15 bolt | Standard 5.56 | Larger bolt face |
| AR15 magazine | Standard AR15 | Dedicated 7.62×39 magazine |
| Ammunition cost | Moderate | Low (steel-case surplus) |
The 300 Blackout follows the ANSI/SAAMI centerfire rifle standard at a 55,000 psi maximum average pressure. 7.62×39 bullets are slightly larger than .308 inch, so the two barrels are not interchangeable.
300 Blackout vs 7.62×39 Subsonic
The 300 Blackout was designed for subsonic loads, and the 7.62×39 was not. A 208 gr 300 Blackout subsonic at 1,020 fps carries 480 ft-lb (Hornady, 16-inch barrel), and 190 to 245 gr subsonic loads are on most shelves. The 7.62×39 has few subsonic loads, and most firearms chambered for it are set up for supersonic gas pressure. For suppressed shooting, 300 Blackout vs 7.62×39 is not close. Read 300 Blackout subsonic.
300 Blackout vs 7.62×39 Supersonic Ballistics
The table compares Hornady’s 110 gr V-MAX in 300 Blackout (2,375 fps, 16-inch test barrel) with Hornady’s 123 gr SST in 7.62×39 (2,350 fps, 20-inch test barrel). Downrange values are Chattahoochee Munitions calculations with a 200-yard zero, standard atmosphere and a 10 mph full-value crosswind, using a G1 ballistic coefficient of .295 for the 7.62×39 bullet.
| Range | 300 BLK 110 gr: energy / drop / wind | 7.62×39 123 gr: energy / drop / wind |
|---|---|---|
| Muzzle | 1,378 ft-lb | 1,508 ft-lb |
| 100 yd | 1,071 ft-lb / +3.2 in / 1.4 in | 1,171 ft-lb / +3.3 in / 1.5 in |
| 200 yd | 821 ft-lb / 0 / 6.2 in | 897 ft-lb / 0 / 6.3 in |
| 300 yd | 622 ft-lb / -13.7 in / 14.8 in | 679 ft-lb / -14.0 in / 15.0 in |
Supersonic, the two are nearly the same in drop and wind. The 7.62×39 load carries about 10 percent more energy, partly because it is measured from a longer test barrel. In a short barrel the 300 Blackout gives up less, since it burns its powder in about 9 to 10.5 inches in Chattahoochee Munitions’ experience. See 300 Blackout ballistics.
The AR15 Difference
This is where most owners decide. A 300 Blackout AR15 uses the standard 5.56 bolt, the standard magazine and the standard lower; only the barrel changes. A 7.62×39 AR15 needs a bolt with a larger face, which leaves thinner lugs, and a dedicated magazine because the tapered case does not feed well from a straight AR15 magazine. The 300 Blackout keeps the AR15 an AR15. Every CM15 uses a TriggerTech AR15 Duty trigger, a Superlative Arms adjustable gas block and an ODIN Works adjustable buffer, so it can be tuned to the load and suppressor. See the 300 Blackout gas system guide.
Ammunition Cost and Choice
The 7.62×39 wins on cost. Steel-case surplus ammunition is cheap, which matters for high-volume practice. The 300 Blackout costs more per round, but it offers a much wider range of bullet weights, from 110 gr supersonic hunting loads to 245 gr subsonic. Black Butterfly Ammunition offers 300 Blackout loads for both. Chattahoochee Munitions does not load either cartridge.
Hunting
For deer and hogs inside about 200 yards, the supersonic loads of both cartridges perform alike with an expanding bullet; for supersonic 300 Blackout, Chattahoochee Munitions offers the 16-inch CM15 with a 1:7 twist. The 300 Blackout adds the option of a suppressed subsonic shot inside about 100 yards with a bullet designed to expand at that speed. For bear, choose a heavier cartridge such as the 375 Raptor or the 458 SOCOM XL. See 300 Blackout hunting.
300 Blackout vs 7.62×39: Which Should You Choose?
Choose 7.62×39 for the lowest-cost supersonic practice, or if you already own firearms in it. Choose 300 Blackout for an AR15 that keeps standard bolts and magazines, for subsonic suppressed shooting, and for short barrels.
300 Blackout Firearms From Chattahoochee Munitions
- CM15 300 Blackout home defense SBR or pistol, 10.5-inch
- CM15 300 Blackout semi-auto SBR, 7.5-inch
- CM15 300 Blackout hog hunting rifle, 16-inch
- CM15-SD 300 Blackout tucked suppressor, 7.5-inch
- CM7S 300 Blackout truck gun, 8-inch
See every configuration in Sector 300.
300 Blackout vs 7.62×39 FAQ
Is 300 Blackout the same as 7.62×39?
No. The cases, bullet diameters and AR15 parts are different. The 300 Blackout is sometimes called 7.62x35mm.
Is 300 Blackout better than 7.62×39?
For subsonic shooting and for an AR15 with standard parts, yes. For low-cost supersonic practice, the 7.62×39 is cheaper.
Which hits harder, 300 Blackout or 7.62×39?
Supersonic, they are within about 10 percent. Subsonic, the 300 Blackout’s heavy bullets carry far more than any common 7.62×39 load.
Can 7.62×39 be fired in a 300 Blackout?
No. The case will not chamber, and the bullet diameter differs. Fire only the cartridge marked on the barrel.
Do 300 Blackout and 7.62×39 use the same magazine?
No. The 300 Blackout uses a standard AR15 magazine. The 7.62×39 needs its own.
Is 300 Blackout or 7.62×39 better for hunting?
They are close supersonic. The 300 Blackout adds suppressed subsonic hunting at short range.
Who makes 300 Blackout firearms?
Chattahoochee Munitions manufactures the CM15 300 Blackout AR15 in 5, 7.5, 10.5 and 16-inch barrels, the CM15-SD, CM15 300 Blackout uppers, and the CM7S 300 Blackout bolt action in 8, 10 and 12.5 inches.