300 Whisper vs 300 Blackout

300 Whisper vs 300 Blackout


Mathew R Reed
August 25, 2021

For firearms owners with a specific interest in rifles, there’s a good chance you’ve heard someone debating whether the 300 AAC Blackout or 300 Whisper is the superior pick.

Although both are considered superior cartridges and designed with much of the same elements in mind, each has its pros and cons.

What is best, the 300 Whisper or 300 Blackout?

The 300 Whisper cartridge is a CIP standard cartridge designed to fire large projectiles at subsonic velocities, and although the original, is considered the lesser-known of the two.

The 300 AAC Blackout is a 30 caliber cartridge that’s been created within the same parameters of the Whisper and is more readily available and used today.

Although they may appear the same on the surface, there’s a good reason why these two rifle cartridges are often debated for greatness.

We’re here to see how the Whisper and Blackout differ and where they’re alike, to help you come up with the best option for your firearm needs.

What is a .300 Whisper?

What is a .300 Whisper?

The .300 Whisper is a type of wildcat cartridge and was part of the Whisper family of cartridges first designed by SSK Industries.

The purpose of its invention was to be a versatile cartridge that could use both lightweight bullets and heavier ones, operating at supersonic and subsonic velocities irrespectively.

The Whisper sometimes goes by other names, including the .300-221 or .300 Fireball, however, they vary in size and pressure.

Although once considered the standard, the .300 Whisper is now lesser utilized today, as other advancements and improvements on its original design have been found, including the .300 Blackout.

What is a .300 Blackout?

What is a .300 Blackout?

The .300 AAC Blackout, sometimes known as the 300 ACC Blackout or 300 BLK, is a rifle cartridge that was designed by Advanced Armament Corporation in conjunction with Remington Defense.

The cartridge was made for use in an M4 carbine with an aim to get the same level of ballistics that the 7.62x39mm Soviet cartridge had in the AR-15 but without having to upgrade the capacity of the standard AR-15 magazine.

Although slightly different, the 300 AAC Blackout was created as a copy of the .300 Whisper and has achieved SSAMI-certification.

As NATO was searching for a round that was greater in subsonic performance than the 9mm and with high velocity, the Blackout was born after years of development.

Their Differences and Similarities

Their Differences and Similarities

If you stacked the .300 Whisper and .300 AAC Blackout next to each other, you’d be hard-pressed to see any noticeable difference at first.

However, although they share many of the same design elements, it’s best to compare these two rifle cartridges in the most important


The price for .300 AAC Blackout ammunition is quite high and it’s still considered one of the more niche rifle cartridges.

If you’re looking to purchase genuine .300 Whisper rounds, you’ll find it even more expensive as it’s not as commercially available today, and considering it’s rated as lesser quality than the Blackout, the need for it has all but vanished.


Ballistics reports are hard to come by on the .300 Whisper due to its lack of popularity today, but the .300 AAC Blackout has a lot of data to decipher.

In terms of power, you’ll be able to get 1,377-foot pounds of muzzle energy from this cartridge when paired with a 10 grain Hornady Black V-MAX.

Speed and Accuracy

Although there are several different ammunition options, the standard 300 Blackout cartridge is capable of muzzle velocity speeds of up to 2,800 feet per second with 78 grain Lehigh Defense CQ ammunition.

This differs drastically from the speed of a .300 Whisper which was designed to be able to reach subsonic velocities, which is under 1070 feet per second, as this helps it to achieve its low noise.


The speed of these bullets isn’t as critical as their accuracy though, with experts claiming that they achieve almost MOA accuracy up to 300 yards.

As they operate in the subsonic velocity, you can expect them to be a lot quieter, so for settings like hunting where stealth is required, both 300 cartridges are ideal.

Where Are They Available?

Where Are They Available?

A quick search for Whisper ammunition will show you just how hard it is to get your hands on, as the rounds have become much less popular these days.

However, the BLK ammunition is also considered a niche round, and because it’s still relatively new in the grand scheme of ammunition, it can be a challenge to find as well compared to some of the better-known AR-15 options.

As Whisper is a registered trademark of SSK Industries, it can be hard to find these specific cartridges on the market.

However, other manufacturers have made their own versions with names like .300 Fireball and 330-221, also designed around the .221 case, making them more accessible and cheaper to purchase as well.

Are They Interchangeable?

300 Whisper vs Blackout

Any time we compare two hotly contested calibers like the 300 Whisper and the 300 Blackout, people want to know if the two are interchangeable.

When it comes to these two, you should be able to load a Whisper into a Blackout chamber safely, but doing it the other way around is considered a no-no.

The reason for this is because the Blackout has a much higher velocity than the Whisper, and it’s also considered a hotter load.

Attempting to put one of these cartridges into the other will lead to permanent damage to the firearm and a potentially risky situation for you as the shooter.

If you do plan on using the two interchangeably, make sure you’ve got the right ammunition for it and some expert advice.

The possibly detrimental effects for your firearm and you will not be worth this type of experiment, so consult a gunsmith or ammunition specialist first.

Which One Is More Popular?

Which One Is More Popular?

There’s no doubt that the 300 Blackout is the more popular rifle cartridge today when you compare the two, even though they’re similar in so many ways.

After the Blackout was released, it became the most successful 30 caliber cartridge and would be seen as the standard option for this size, with the .300 Whisper becoming less popular.

Today, this commercial popularity remains and the .300 AAC Blackout has become a household name in carbine cartridges.

Although the Whisper doesn’t have the same type of name recognition, most rifle enthusiasts still know the origins of it and may be able to still purchase the cartridges from some places.

In terms of quality, the Blackout is considered the better option as well, so it’s not just about which one is more popular among shooters.

The brass dimensions of the Blackout rate it as just a bit bigger, with 0.004 inches more height in the neck and an 0.018-inch longer case.

Furthermore, because the Whisper is part of the wildcat family of cartridges and the Blackout has its SAAMI standardization, the Blackout is the winner.

The Ultimate 300

The .300 Whisper and .300 AAC Blackout might not be as hotly contested as they used to be when it comes to performance and quality, but it’s still interesting to look back at their development and see how they differ.

It’s clear that the 300 BLK is the rifle cartridge of choice today, with the Whisper becoming almost obsolete in recent times, although one wouldn’t exist without the other, so it’s always good to pay your respects.

Related Questions

There are countless options out there for calibers and rounds, each of them offering something unique to the gun itself.

If you’re still unsure about choosing the right caliber for the situation, check out these commonly asked questions and our expert answers to help you out.

What Caliber Rifle is the Fastest?

If velocity is your priority when choosing a rifle caliber, the .220 Swift is considered one of the fastest commercially available cartridges in the world.

The .220 Swift records speeds of around. 4,665 feet per second when fired with a 29-grain bullet in the right conditions, which puts it miles ahead of the competition.

How Do I Tell What Caliber My Rifle Is?

The caliber of a rifle is usually stamped somewhere on the barrel, otherwise, you may be able to measure the inner diameter of the barrel for a vague idea.

If you’re unable to locate an official mark or stamp, taking the firearm to a gunsmith for clarification is the safest way forward.

What Are the Best Rifle Caliber for Big Game?

Big game hunting requires a powerful caliber, with some of the more popular options being .243 Winchester, 6.5 Creedmor, 7mm-08 Remington, just to name a few.

For this setting, you want a long-range compatible cartridge and one that will deliver enough power to take down a large animal humanely in one hit.


Mathew R Reed

Mathew R Reed is a professional gun seller who runs a dedicated gun store in the suburbs of Oakland, CA. A hardcore hunting enthusiast since childhood, Reed has ample experience with guns and accessories. He is the founder of ArmorHoldings.com and creates some of the most helpful gun-buying guides and explainers. If not in the gun shop, you can find him on the nearest hiking trail or nearby hunting spot.