Why subsonic matters
A suppressor reduces muzzle blast. A bullet traveling faster than the speed of sound makes its own sharp "crack" along its whole flight path, and no suppressor can stop that. Subsonic ammo keeps the bullet below that threshold, which is about 1,125 fps at sea level in mild weather. The speed of sound drops in colder air, so a load that's comfortably subsonic in summer can come close in winter.
.22 LR
Many standard-velocity .22 loads sit near the speed of sound, and a long rifle barrel can push some over it. Dedicated subsonic loads leave more margin. The catch: lighter loads may not cycle every semi-auto.
CCI .22 LR 40gr subsonic LHP
Aguila .22 LR 40gr subsonic SP
Remington .22 LR 40gr subsonic HP
Pairs with: FN 502 Tactical, X-Ring, SU22. More at RimfireAmmo.
9mm
Most 115gr and many 124gr 9mm loads are supersonic. 147gr loads are the standard subsonic choice, and some are made specifically for suppressors (Winchester Super Suppressed, for example). Note that pistol-caliber carbines add velocity from their longer barrels, so confirm your load stays subsonic from a carbine.
US Cartridge 9mm 147gr subsonic FMJ
Winchester Super Suppressed 9mm 147gr
Hornady Subsonic 9mm 147gr XTP
Pairs with: FN 509 Tactical, Ruger PC Carbine.
.300 Blackout
The cartridge was designed around heavy subsonic bullets. 200–220gr loads are well below the speed of sound from common barrel lengths. Cycling in gas guns varies, so test suppressed.
Magtech .300 BLK 200gr subsonic FMJ
Federal AE .300 BLK 220gr subsonic OTM
Winchester Super Suppressed .300 BLK 200gr
US Cartridge .300 BLK 220gr subsonic FMJ
Pairs with: CMMG Banshee and Dissent, Savage 110 Scout. See .300 BLK pistol vs rifle.
Testing checklist
- Shoot with the suppressor attached, since cycling can change.
- Try at least two or three loads.
- Note point-of-impact shift with and without the can.
- Re-check performance in cold weather if you shoot year-round.
Subsonic ammo
category
Frequently asked questions
What is subsonic ammo?
Ammunition loaded so the bullet travels slower than the speed of sound, about 1,125 fps at sea level in mild temperatures. That avoids the supersonic 'crack.'
Can barrel length make subsonic ammo supersonic?
It can, if the load is close to the threshold. Longer barrels can add velocity. This matters most for some .22 LR loads in rifles.
Will subsonic ammo cycle my semi-auto?
Not always. Lighter subsonic loads may not cycle some guns, especially .22 pistols and some gas guns. Test your load.
Is subsonic ammo good for defense?
Some subsonic loads use expanding bullets, like 147gr 9mm hollow points. Choose loads designed for defense if that's the use.
Keep reading
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