Silencer Ammo

Why Subsonic Ammo Is Quieter

When a bullet travels faster than the speed of sound, it creates a small sonic boom — the distinctive crack you hear when a shot is fired. A suppressor reduces the muzzle blast (the gas escaping the barrel), but it does nothing to eliminate the supersonic crack of the projectile. Subsonic ammo eliminates the crack entirely by keeping the bullet below 1,125 fps. The result, when used with a quality suppressor, is a noise level closer to a pneumatic nail gun than a gunshot. For some calibers like .45 ACP and .300 Blackout, subsonic loads are standard; for others like 9mm and .308, you’ll need to specifically select subsonic loads.

Best Calibers for Subsonic Shooting

.300 Blackout was specifically designed around subsonic performance and is the gold standard suppressor-host rifle caliber. Standard .300 BLK subsonic loads run 220gr bullets at around 1,000 fps, cycling reliably in AR-15 pattern rifles with an adjustable gas block. .45 ACP is naturally subsonic with standard loads, making any .45 ACP pistol a capable suppressor host without special ammunition. .22 LR subsonic loads like CCI Quiet and Standard Velocity are extremely popular for suppressed rimfire shooting — very quiet, inexpensive, and widely available. 9mm subsonic loads (typically 147gr+) are the most common suppressor-host pistol caliber.

9mm Subsonic Loads

Standard 9mm runs 115–124gr bullets at 1,150–1,200 fps — supersonic. For suppressed 9mm, look for 147gr or heavier loads at 900–1,000 fps. Hornady Subsonic 147gr XTP, Speer Lawman 147gr TMJ, and Federal American Eagle 147gr are reliable subsonic 9mm options. Heavier 158gr and 165gr loads are also available and guaranteed subsonic. Keep in mind that some pistols may cycle less reliably with very light powder charges — test your specific gun before depending on any subsonic load.

.300 Blackout Subsonic

The .300 BLK platform was engineered for subsonic suppressed use, and the caliber truly shines in this role. Hornady 208gr A-MAX, Remington 220gr OTM, and SIG Sauer 220gr Elite Performance are purpose-built subsonic loads. At 1,000 fps, a 220gr .300 BLK projectile carries considerable energy for close-range use while remaining extremely quiet suppressed. The main consideration is gas system tuning — most .300 BLK rifles need an adjustable gas block to cycle reliably with both supersonic and subsonic loads.

.22 LR Subsonic

Suppressed .22 LR is one of the most enjoyable and affordable shooting experiences available. CCI Standard Velocity (1,070 fps) and CCI Quiet (710 fps) are the most popular subsonic rimfire loads. The Quiet load is so mild it won’t cycle most semi-auto .22s, so it’s best suited for bolt-actions and single-shots. Standard Velocity will cycle most semi-autos and is still subsonic at standard temperatures. A quality .22 suppressor with standard velocity ammo produces a noise level comparable to a screen door closing.

Frequently Asked Questions: Suppressor Ammunition

What makes ammunition good for suppressor use?
Subsonic ammunition stays below the speed of sound (approximately 1,125 fps) and eliminates the supersonic ballistic crack that a suppressor cannot reduce. When paired with a quality suppressor, subsonic loads in 9mm, .45 ACP, .300 Blackout, and .22 LR can produce hearing-safe or near-hearing-safe sound levels. Supersonic ammunition through a suppressor is still significantly quieter than unsuppressed — hearing protection is often not required for occasional shots — but the ballistic crack remains.

What is the quietest caliber for a suppressor?
.22 LR subsonic is the quietest common suppressed configuration — standard velocity .22 LR (1,070–1,080 fps) is naturally subsonic from most barrels and produces hearing-safe levels through a quality suppressor. 9mm subsonic (147gr at 900–950 fps) and .45 ACP (which is inherently subsonic at standard velocities) are the quietest suppressed centerfire pistol calibers. .300 Blackout with 220gr subsonic ammunition is the quietest rifle configuration.

Do I need special ammo for a suppressor?
No — you can use standard ammunition through most suppressors. However, subsonic loads maximize the sound reduction benefit of the suppressor. Standard supersonic ammunition through a suppressor is quieter than unsuppressed but retains the ballistic crack. For hearing-safe use, subsonic ammunition is necessary. Always verify your suppressor is rated for the specific caliber and pressure level you intend to use.

Will subsonic ammo cycle my semi-automatic reliably?
Subsonic pistol loads (9mm 147gr, .45 ACP standard velocity) typically cycle standard semi-automatics reliably — these are within normal operating parameters. Subsonic rifle loads (.300 Blackout 220gr) require a dedicated subsonic-optimized gas setting on adjustable-gas rifles or a suppressor host specifically designed for subsonic cycling. Standard direct-impingement AR-15s may need an adjustable gas block to cycle heavy subsonic loads reliably.

See Also: Suppressors & NFA • .300 Blackout Ammo • 9mm Ammo • .22 LR Ammo • How to Buy a Suppressor