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9×39 mm vs. .300 AAC Blackout: Cartridge Showdown—Now With the Right Rifles

  • Writer: Admin
    Admin
  • May 6
  • 3 min read

Intended Platforms at a Glance

Cartridge

Native Platform

Operating System

Typical Barrel Length

Suppressor Friendly?

9×39 mm

Gas‑piston AK variants (VSS Vintorez, AS Val, modern AK‑9)

Long‑stroke piston

200‑240 mm (7.9‑9.4")

Purpose‑built integral or thread‑on

.300 AAC Blackout

Direct‑impingement AR‑15 (simply swap barrel)

DI (or short‑stroke piston)

230‑410 mm (9‑16")

Designed around detachable cans

Ballistics & Velocity: How the Same Round Behaves in Different Guns

Load (factory)

Test Barrel

Muzzle Velocity

Muzzle Energy

9×39 mm 16 g (247 gr) SP5

230 mm VSS barrel

295 m/s (968 fps)

1,390 J

9×39 mm 16 g SP5

410 mm custom AR barrel

325 m/s (1,066 fps)

1,650 J

.300 BLK 220 gr OTM

305 mm (12") AR‑15 DI

308 m/s (1,010 fps)

1,475 J

.300 BLK 220 gr OTM

240 mm AK‑102 conversion

285 m/s (935 fps)

1,290 J

Reliability & Parts Availability

Build

Feed Reliability

Parts Cost & Availability (U.S.)

Magazine Options

Native AK 9×39 (Kalashnikov USA, PSAK‑VDB import)

Excellent—tapered case & generous chamber

$$$; limited domestic barrels/bolts

20‑ or 30‑rd 9×39 double‑stack

Custom AR‑15 9×39

Good if you use C‑39 or Faxon bolts and true 9×39 mags

$$; barrels & bolts niche but online

ASC 20‑rd steel 9×39

Native AR‑15 .300 BLK

Excellent; any .223/5.56 mag works

$; barrels everywhere

30‑rd STANAG →

Custom AK .300 BLK (Krebs, Meridian)

Good once gas tuned; straight‑walled case can nose‑dive

$$‑$$$; custom barrel & reamed bolt

Uses standard 7.62×39 mags (load to 25 rd)

Suppression & Signature


·       Sound: Both keep peak SPL under ~135 dB with a quality 8‑inch can, but 9×39’s heavier bullet yields a lower frequency “thud” that many describe as quieter to the ear.


·       Flash: 9×39 in an AR shows more unburned powder at the muzzle (Russian powders are slower), while .300 BLK in an AK produces slightly more visible flash because the shorter barrel trims burn time.


·       Recoil: Felt recoil in comparable SBRs is a wash; 9×39 edges softer in piston guns thanks to a heavier carrier moving slower.


Cost & Ammo Logistics (U.S. Market, Q2 2025)

Round

Street Price (per 20)

Import / Domestic

Current Availability

9×39 mm

$32‑40

Imported (Red Army, Tula)

Intermittent—sanctions sensitive

.300 AAC BLK

$22‑28 (subs)

Largely domestic

Plentiful; dozens of SKUs

So, Which Cartridge and Which Rifle?

Use Case

Best Pairing

Why

Whisper‑quiet predator/pig hunting to 150 yd

AR‑15 .300 BLK with 10‑12" barrel

Same controls as your 5.56 rifle, cheap ammo, plentiful mags

Urban CQB or suppressed patrol carbine

AK‑based 9×39 (PSA AK‑VDB)

Sub‑sonic punch through intermediate barriers, piston reliability

Tinkerer’s wildcat fun

AR‑15 9×39

Easy barrel swap, more velocity than Russian SBRs

AK purist who reloads

AK .300 BLK conversion

Shares cheap brass but keeps AK ergos & piston cleanliness

Final Thoughts


Adding the rifle into the equation shows why each cartridge shines in its home field—and how far you can push them in someone else’s stadium. 9×39 in a purpose‑built gas‑piston AK delivers big‑slug terminal energy and unstoppable reliability, but parts and ammo carry import headaches. .300 AAC Blackout in an AR‑15 remains the king of availability, modularity, and magazine interchangeability.Exotic builds prove both rounds are flexible, yet they also expose the tuning, magazine, and cost hurdles you’ll face. Decide first what handling characteristics you want, then choose the cartridge‑platform combo that gets you there with the fewest compromises.


Next Step


Need honest, hands‑on advice—and perhaps a vetted parts list—before you start threading barrels or ordering obscure magazines? Contact The Jewelry Liquidation Guru (yes, we’re also firearms nerds) and we’ll help you stretch every dollar while building the quiet carbine of your dreams.

 
 
 

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