velocity Archives

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.

typical pistol cartridges (left) with a couple rifle cartridges (right). Even though all these cartridges have similar bullet weights, the velocities are around double from rifle rounds.

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.

Moist air has visible effects as well as invisible effects

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.

This image shows both the sound waves caused by the bullet, as well as the waves coming from the unsuppressed muzzle

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.

Culling some pest turkeys in suburbia is better done suppressed and subsonic, this was done with the **TX22** and a **Silencerco suppressor**

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.

This buck fell to a single shot from a subsonic 450 Bushmaster, a **405 grain solid lead-cast bullet** with a flat meplat. The sound of the bullet impacting the deer was much louder than the gun going off. My **Desert Tech MDRX**

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.

My **Desert Tech SRS** A1 Covert with a 16″ 1:3 twist 8.6 Blackout barrel and **Anechoic suppressor**

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.

Its easy to see why the 308 Winchester (top) can achieve much higher velocity than the 300Blk (bottom) when both are shooting supersonic 150 grain bullets

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.

This fox was far too brave, walking between us in camp in the dark. A subsonic 308 quietly put him out. And later that day, the same rifle (different ammo) was used to shoot a cow elk 200 yards away.

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.

Suppressed subsonic 22 pistols are very handy for dispatching pests, this one is another **Taurus TX22** with a **YHM Phantom** suppressor

Don’t miss the video at the end of this article

With modern rifles and bullets, the distances we shoot at animals keeps creeping further and further out. But as bullets travel further away, they lose more and more velocity. How much they lose, and how fast they impact is a very important subject when it comes to cleanly killing an animal. We’ve killed many animals over the years, and its an interesting and important subject. And one particular instance is one I’d like to discuss today.

Last fall, a friend of mine shot a small deer at 900 yards with a 6.5 Creedmoor using a 143 ELDX. This was certainly towards the end of the envelope of energy and velocity for that combo, but it did the job as good as one could hope. The deer took a single shot quartering away, the impact hit just behind the rib cage and passed completely through the animal, exiting through the front of the chest. The heart was punctured, and the deer made it about forty yards before tumbling down the hillside. Everything looked textbook as far as killing it cleanly and quickly. The impact velocity was right around 1800 FPS which according to Hornady should have been enough to open the bullet.

After much hiking to get to the deer, we found a massive blood trail and a perfectly perforated buck. We retraced his steps, as well as the video we recorded looking to see all the details. I was absolutely amazed when as we stood there recounting the events, I looked down to see the bullet laying there in the dirt, not far from where the deer lay dead. The bright copper shown against the damp hillside. Even though the bullet had hit a rock after exiting the deer, it had come to rest nearby. Our immediate impression was “that doesn’t look right”. The bullet had barely opened at all, it had only lost its plastic tip, and bent the front of the bullet off to one side. On further inspection back at the house, the bullet weighed 142.3 grains. Probably just the weight of the lost plastic tip.

The recovered 143 ELDX weighed 142.3 grains

Despite the bullet not opening as best we could tell, it still did plenty of damage. But it seems the 1800 FPS in this instance wasn’t enough to cause sufficient deformation of the bullet. This is one of the reasons I like to use “softer” bullets when shooting long-range, they are much easier to rupture.

Note the hole through the heart of the deer mentioned

Impact velocity greatly effects the bullets ability to do damage. I have found several bullets in elk over the years, that obviously didn’t do the job. Whoever shot those bullets may still be scratching their head wondering what happened. Bullets can fail to perform just like anything else, which is one reason why I stress shot placement so often. This event is a perfect example why, even though the bullet did not rupture as designed, it still made a hole through the most vital of organs, causing a quick death for the animal in question.

Distance to the target, and the impact velocity of any given bullet is just one of the many things marksmen need to take into account when evaluating a firing solution. Another anecdote featuring the same bullet; a friend of mine shot a cow elk at approximately 600 yards, the bullet impacted broadside passing through both lungs and stopping in the offside shoulder. Again this one had lost its tip, and barely opened. The cow made it into the trees a few dozen yards, where it lay down and expired. In this case one would surely expect the bullet to have opened, as the impact was likely in the 2200 FPS range. And again, due to good shot placement, it worked despite the bullet not opening.

These are of course a couple of anecdotal examples, and surely not a full representation of this particular bullets performance. But it is certainly food for thought, and something to keep in mind. I have gone into much more detail on the subject in this article about shot placement, I’d invite you to read that one as well, and we can carry on the discussion.
I hope these discussions are helpful, the game we hunt deserve the best skillset we can prepare to avoid undue suffering.

-CBM