Introduction

More and more often, we are seeing interesting developments when it comes to bullets and ammunition. Today I wanted to discuss an interesting situation regarding velocity of bullets, and how specialty designed slower cartridges are changing the future of shooting. Are subsonic cartridges superior? Well, depending on your purpose they just might be.

The velocity of a bullet when fired from a firearm has a lot to do with its utility and purpose. Most rifle bullets travel at supersonic speeds, that means they travel faster than the speed of sound. Conversely, many handgun bullets travel near or below the speed of sound. For the most part, this has been a result of typical construction limitations for both firearm and ammunition manufacturing. Handguns typically have less room for large powder capacity cartridges, which is why they are typically slower. Which is also why rifles often have much higher velocities, as rifle cartridges often have more room. Additionally, rifles need greater range than most pistol cartridges, which has resulted in their design for more velocity.

What is the Speed of Sound?

The speed of sound is determined by how fast a sound wave travels through air. We have all witnessed curious situations where we see something far off before we hear the sound. That is because the sound takes much longer to get to us than the light reflecting the image to our eyes.

To add another layer of complexity, not all air is the same. The speed of sound is relevant to the current atmosphere the sound is traveling through. Humidity and air pressure can greatly effect air density and therefore the speed of sound will change depending on the atmospheric conditions. For example; warm dry air will result in a higher speed of sound than cold humid air.

Why does this matter? Because bullets also travel through air, and they are also equally effected by atmospheric conditions. As a bullet travels through the air it encounters resistance, and much like a boat traveling through water, once it starts moving fast enough it creates a wave. The pressure wave caused by bullets traveling faster than the speed of sound creates a sonic boom. This is why even when using a suppressor, most rifles are still quite noisy. Because the bullet itself is breaking the sound barrier which is quite loud. The suppressor removes most of the noise caused by the report of the rifle, but the supersonic bullet causes its own noise.

Subsonic bullets, those that travel below the speed of sound do not create the pressure wave or sonic boom. Much like a boat that idles across a lake doesn’t make much of a wave. And if you use a suppressor to remove the report of the firearm, these bullets can be fired pretty quietly. Almost like you see in the movies, just less stupidly.

Why would you want Subsonic vs. Supersonic?

Subsonic shooting with a suppressor can be very fun, and extremely useful if you are a hunter. Shooting a whole pack of coyotes could be doable with marksmanship and such silent shooting. The appeal of this covert shooting ability has enticed many shooters and engineers alike. Which has resulted in various new firearms and ammunition lines that are specifically designed for this purpose. Cartridges like the .300 Blackout and 8.6 Blackout have received a great deal of attention lately as suppressor use has skyrocketed. The use of these cartridges with a suppressor has made super silent shooting a reality, and it has become very addicting to those who practice it.

It is important to understand the limitations of these specially designed products. There are ammunition lines and even cartridges that are specifically designed for subsonic use. Purpose built subsonic cartridges and bullets tend to have more limitations because of velocity. In order to maintain their speed below the speed of sound there are few ways to add energy other than increasing the size of the bullet. Some folks like those at Discreet Ballistics have designed solid copper expanding bullets, to increase the transfer of energy on impact. Another theory though disputed by some; is that increasing the rotational speed of the bullet can add energy on target. This is achieved by using fast twist barrels like one-in-five, one-in-three or even as fast as one-in-one twist barrels.

The lower velocity of these bullets can greatly alter the effectiveness of them at extended distances. While it can be done, subsonic cartridges are much more susceptible to variations. And those variations are more pronounced as you cover more distance. The anonymity of super quiet shooting can be very valuable, but requires an extra level of understanding to know when and where it can be applied effectively.

Standard Cartridges Too

Standard cartridges can also be down-loaded to subsonic speeds, particularly those that aren’t that fast to begin with. I used to load my 308 down with subsonic 220 grain bullets, and they were fun, and quite useful.

I’ve also loaded my 450 Bushmaster down to subsonic speeds and increased the bullet weight significantly for added performance. There is an added benefit to this scenario, a 308 can shoot subsonic bullets much like a 300Blk, but it can shoot much better when loaded with supersonic ammunition. A subsonic 220 grain bullet fired from a 308 chamber vs. a 300Blk chamber will fly the same all else being equal. But say you want to increase your energy on target and distance by changing bullets and powders for supersonic use. A 165 grain bullet fired at supersonic speeds from a 300Blk will be nowhere near as fast as one fired from a 308 chamber, all else being equal.

What Not to Do

Many manufacturers have jumped into making firearms chambered for some of these dedicated subsonic cartridges. And that has resulted in a great deal of adoption by folks from every walk of life. It should come as no surprise that some are shooting dedicated subsonic cartridges and ammunition through firearms without a suppressor. While they are perfectly happy doing it, they certainly aren’t getting the bang for their buck. Shooting unsuppressed with subsonic cartridges like the .338 ARC or .300BLK is like wearing flip-flops to go hiking. The greatest asset of these cartridges is shooting silently with a suppressor, so if you aren’t going to use a suppressor, why cut your velocity, energy and range for no gain? Perhaps you might have another reason, but anything you can do with a subsonic .300Blk can be done better and for less with something like a 5.56 or 6ARC. The best advantage of the Blackout is its silent shooting, so if you’re going to shoot loud, you may as well shoot something better.

The Right Application

As you might have gathered by now, there is a perfect application for subsonic shooting. A scenario where you need exceptionally quiet shooting, whether that be dispatching pests or something else. For example; a subsonic 22lr is great for taking out rats covertly in the dark. And if you use the slightest bit of imagination you’ll come up with other ideas. It is these specific scenarios where a subsonic cartridge is superior to supersonic options.