We’re on the hunt for the quietest .300 Blackout ammo to use with a suppressor!

If you’re trying to find quietest ammo for your .300 BLK build, we’re here to help. We decibel test nine different .300 BLK loads at the range using a professional decibel reader in search of the quietest round!

Decibel Testing .300 Blackout Ammo

We rented a Larson Davis Spartan 821 Noise Sound Level Meter for our testing, and set it up using a .25″ microphone set up one meter to the left of the shooter.

We used 3GunKenzie‘s custom .300 Blackout setup as our test gun:

• Tactical Kinetics 5” 300 BLK Barrel
• TiON Dragoon 7.62 QD Mini Suppressor
• Daniel Defense Lower
• Black Fire Forge Upper

It’s worth noting that this custom build may be a bit louder than a build that uses an 8″ to 10.5″ barrel length. Many shooters build their own .300 Blackout rifles and pistols, so you should know that your results will be different in your own build.

We test nine different types of .300 Blackout ammo. For each load tested, we shot five rounds each. We then took the average z-weighted decibels for those shots. When measuring gun shots for potential hearing damage, we use z-weighted decibels (dBZ), or linear or unweighted, for the most accurate measurement.

For comparison, some common average decibel ratings from the National Institute on Deafness and Other Communication Disorders include:

• Normal conversation
  60-70 dBA
• Movie theater
  74-104 dBA
• Motorcycles and dirt bikes
  80-110 dBA
• Music through headphones at maximum volume, sporting events, and concerts
  94-110 dBA
• Sirens
  110-129 dBA
• Fireworks show
  140-160 dBA

From this test and our .22LR decibel test and 9mm decibel test, the average recorded decibels for each gun with all ammo tested were:

• .300 Blackout Suppressed: 134.18 dBZ
• 9mm Pistol Suppressed: 128.02 dBZ
• 9mm Pistol Unsuppressed: 157.42 dBZ
• 9mm PDW Suppressed: 131.05 dBZ
• .22LR Pistol Suppressed: 116.53 dBZ
• .22LR Pistol Unsuppressed: 143.9 dBZ
• .22LR Rifle Suppressed: 113.11

Fiocchi 300 AAC Blackout Ammunition - 500 Rounds of 125 Grain SST

$499.99

Sellier & Bellot Subsonic 300 AAC Blackout Ammunition - 20 Rounds of 200 Grain FMJ

$19.99

Quietest .300 Blackout Ammo

From our testing, the top 5 quietest .300 Blackout ammo loads were:

1. Hornady Black 208gr. A-MAX
2. Black Hills Subsonic 220gr. OTM
3. Fiocchi Subsonic 220gr. HPBT MatchKing
4. Hornady 208gr. BTHP
5. Underwood Subsonic 220gr. HPBT

We’ll take a closer look at the top five rounds from our test below.

Hornady Black 208gr. A-MAX

• Average Decibels: 132.48 dBZ
• Advertised Velocity: 1020

Hornady designed the Hornady Black 208gr. A-MAX for accuracy, but it also runs very quietly through our suppressed setup. 

Black Hills Subsonic 220gr. OTM

• Average Decibels: 133.26 dBZ
• Advertised Velocity: 1000 fps

While technically the Black Hills Subsonic 220gr. OTM made it to #2 on our list of quietest .300 Blackout rounds, at the range we noted that it seemed rather loud. 

Fiocchi Subsonic 220gr. HPBT MatchKing

• Average Decibels: 133.5 dBZ
• Advertised Velocity: 1020

Fiocchi loads their Subsonic 220gr. HPBT MatchKing round with the extremely accurate Sierra MatchKing projectile. 

Hornady 208gr. BTHP

• Average Decibels: 133.9 dBZ
• Advertised Velocity:

This load from Hornady is often outshined by the similar 208gr. with an A-MAX bullet that made our number 1 spot. However, this specific load is no longer manufactured anymore, though you will sometimes find it being sold at big retailers. If you come across this round, it may be worth picking up a couple boxes.

Underwood Subsonic 220gr. HPBT

• Average Decibels: 134.22 dBZ
• Advertised Velocity: 1030

The Underwood Subsonic 220gr. HPBT was our 5th quietest load tested. While it is a hunting round, it also offers the accuracy of a match load.

Other .300 Blackout Options

Since one of our top five is no longer widely available, and another we were not impressed with at the range, I wanted to throw in the two options that tied for 6th place.

The Hornady Subsonic 190gr. SUB-X and Super Vel Hush Puppy 200gr. FMJ both registered average decibels of 134.62dBZ. While they have lighter bullet weights than our top five, they were also both tied for crowd favorite when we did a blind comparison of rounds.

Quietest .300 Blackout Ammo: Final Thoughts

There are many other .300 Blackout loads that we didn’t get the opportunity to test. And while the data from the decibel reader is nice, what really matters when comparing these rounds with similar decibel levels is how they sound to the ear.

So, rather than just looking at decibel levels, it may be helpful to see how the loads compare to each other when shopping for quiet .300 BLK ammo for your gun.

Fiocchi 300 AAC Blackout Ammunition - 500 Rounds of 125 Grain SST

$499.99

Sellier & Bellot Subsonic 300 AAC Blackout Ammunition - 20 Rounds of 200 Grain FMJ

$19.99