What Is Subsonic Ammo?

Ammunition comes in hundreds of different calibers and grains. Although most ammunition on the market is supersonic, subsonic ammo is becoming increasingly popular. Why would someone want slower ammunition? Well there are a few reasons, but the largest is likely to be used with a suppressor. Due to the popularity of suppressors, plenty of shooters are looking for subsonic ammo to pair with them.

Subsonic ammunition travels at a velocity slower than the speed of sound.  This slower speed prevents the bullet from making a supersonic shock wave (sonic boom) as it travels. The speed of sound is 1125.33 fps. Subsonic ammunition is loaded to operate at speeds under 1125.33 fps.

Subsonic ammo can be purchased or produced for many handgun and rifle calibers. The choice to shoot subsonic ammo should be directly related to the use of the firearm and the goal of the shooter. Today I will answer the most common questions around subsonic ammunition and when you should and shouldn’t use it.

Is Subsonic Ammo Silent?

Subsonic ammunition is simply a bullet that travels at a slower speed than the speed of sound. The speed of sound is roughly 343 meters per second (about 1125 feet per second), although it can change slightly depending on elevation and weather factors. A bullet traveling at a velocity less than this eliminates the audible shock wave sound.

This is just part of the equation of the overall sound heard when a bullet is fired in reality. The other audible noise that is heard comes from the expanding gasses escaping the bore of the gun. This is what suppressors are designed to help eliminate.

A subsonic bullet eliminates the downrange “crack” of the bullet. When paired with a suppressor, the muzzle “bang” of the escaping gasses is greatly reduced. This results in the quietest shooting firearm you can possibly have.

Keep this in mind; just because ammo is labeled subsonic doesn’t mean it will be where you are shooting. In colder temperatures, the speed of sound is reduced and the opposite occurs at higher temperatures. This may be just enough to cause the bullet to produce a sonic boom if your ammo is just under 1125 per second in usual conditions.

Should You Hunt With Subsonic Ammo?

Subsonic ammunition is not recommended for hunting big game, nor is it the best choice for small game, with one exception being a .22LR. The big factor when deciding whether or not to use a certain caliber and bullet to hunt with is the amount of stopping power or foot-pounds of energy that the cartridge will produce.

Subsonic ammo is slower which makes it have less energy than its supersonic counterpart. Kinetic energy is calculated by mass times velocity squared. In short, a slower bullet will have less kinetic energy than a faster one of the same weight. This is important to keep in mind. Velocity reduction can make what should be a caliber suitable for deer hunting into one that produces only enough energy to harvest small game. 

Rimfire Subsonic Ammo 

Rimfire rifles, specifically the .22 LR are much more suited for subsonic ammo. At longer distances, the heavier subsonic bullet remains ballistically stable whereas a supersonic .22 would begin to tumble. 22 LR isn’t going screaming fast to begin with, so subsonic ammo isn’t too far of a stretch.  

As far as hunting with subsonic .22 LR ammo, a supersonic load will travel at a velocity of around 1200 feet per second. This delivers around 140 foot-pounds of muzzle energy. When using a subsonic round, it reaches a velocity of around 1050 feet per second delivering 100 foot-pounds of energy. That is plenty of kinetic energy to ethically harvest small game.

Kinetic Energy Required for Deer

Ideally, a deer rifle will shoot a bullet that hits with 1,000 foot-pounds of energy. This has become the standard number that deer hunters go by. There are plenty of calibers out there that may be used to hunt large game using subsonic ammo, but shot placement and range are limited when using them.

One of the more common subsonic rifles is the .300 Blackout. This caliber is designed to shoot both subsonic and supersonic ammo. Even this specially designed caliber will not produce the ideal amount of energy for deer hunting. For example, a subsonic 208-grain bullet will only deliver about 480-foot pounds of muzzle energy. It is only effective on deer with the correct shot placement and at short range, preferably within 50 yards.

Bullets designed for big game will not expand at subsonic speeds. This is another issue with using subsonic rounds for big game hunting. Bullet expansion is vital for quick ethical kills. Without it wound channels remain small which leads to worse blood trails. 

Yes, it is possible to hunt big game with subsonic ammo, but it is not recommended. I wouldn’t use it with the intent of not spooking other deer when you shoot. They will spook anyway, and they hear a lot better than we do. If you want an example, just watch any bow hunting show. For the everyday hunter, the best bet is to use supersonic ammo for all big game hunting applications.

Common Calibers to Use Subsonic Ammunition With

There are many calibers that subsonic ammo can be purchased for. The most common calibers subsonic cartridges used are 9mm, .45ACP, .300 Blackout, and .22LR. Of these calibers, the only one inherently subsonic is the .45ACP. The only one that benefits from subsonic ammo ballistically is the .22LR.

Probably the most common caliber to use subsonic ammo with is a .22LR. When subsonic ammo is used in a .22LR there are actually advantages regarding ballistic performance. Competitive .22LR shooters almost always choose the heavier subsonic rounds.

The newest caliber on this list and the one gaining the most popularity is the .300 Blackout. Like the.22LR it performs with subsonic ammo and is designed to do so. There are sacrifices in stopping power and effective range, but when combined with a suppressor this is about as quiet a rifle as you could ever shoot.

Due to a higher demand for subsonic ammo which is directly related to increased demand in suppressors, many ammo manufacturers are beginning to produce subsonic ammo for even more popular calibers such as the .45-70 Gov’t, .350 Legend,.450 Bushmaster, and many others.

I’d also like to mention that just because subsonic ammo is offered for many different calibers doesn’t mean it will perform the same out of any caliber. In reality, shooting subsonic ammo limits the performance of your firearm, whether it be accuracy, stopping power, effective range, or all of the above.

Can You Use Subsonic Ammo in Your Firearm?

The short answer to this is yes. You could, in theory, load a subsonic round or purchase one for the caliber of your firearm with a few exceptions. Just because you can doesn’t mean you should or that it would be safe to do so.

If your firearm of choice is a semi-automatic, subsonic ammo oftentimes will not cycle. You are limiting yourself to bolt-actions, pumps, single shots, and revolvers. In the case of a revolver you limit the ability to add a suppressor that will be effective. 

As far as accuracy, not only do you need to realize that there is going to be more drop with the slower bullet, but you want a barrel with a high twist rate. In order to consistently make precise and accurate shots, a higher twist rate is necessary to stabilize the bullet.

Some calibers are just not fit for subsonic ammo. For example the .300 magnums and .338 Lapua are cased so big that it is not possible to produce consistent subsonic loads. The newer and possibly most popular recent caliber, the 6.5 Creedmoor, would be pretty much useless as a firearm if loaded subsonic.  

If you just want to have some fun with subs, by all means, load them up. Although if you want to do some serious shooting, you need speed. You will not see any competitive high powered rifle shooters using subsonics. 

Benefits of Subsonic Ammo

The only real benefit of using subsonic ammunition over supersonic ammo is that it is noticeably quieter, especially when used with a suppressed firearm. These slower rounds also produce less recoil.

A subsonic bullet combined with a suppressor is substantially quieter than a supersonic round shot through an unsuppressed firearm. Because of this, it is widely used for pest control applications. They are especially popular in areas where disturbances must be kept to a minimum.

Subsonics paired with a suppressor are also used by hunters that are removing nuisance animals, like feral hogs. Quieter rounds can in theory help you remove as many pigs as possible in one area. A suppressor paired subsonic ammo dampens the sound so much that other pigs will not immediately spook, which gives hunters a chance to take more pigs.

Reduction in recoil is also a benefit, especially when introducing new shooters to the sport or when shooting many rounds at a time at the range. Less recoil will allow for a new shooter to shoot more comfortably and hone their skills at the range before they take it to the next level and possibly into the field. 

Supers or Subs?

The short answer is supersonic ammo is superior to subsonic ammo. There are some applications other than competition .22 shooting that may be better suited for using subsonic ammo. If your goal is to have the quietest shooting gun out there, then subsonic ammo is no doubt the way to go. When combined with a suppressor, you will have the quietest shooting firearm there is. 

If you are thinking about subsonic ammo for your firearm that you use to hunt big game, then you are thinking too hard. Just stay away from subsonic ammo. The decreased stopping power and effective range mean that you are limited on shot opportunities and you will have a greater chance of wounding an animal. It is not worth the risk.

As far as small game hunting is concerned, there are really no downfalls to using subsonic ammo. It still provides plenty of energy to ethically harvest small game animals.

If you have a firearm strictly for close range self-defense, subsonic ammo will do what you need it to do. Although you will be sacrificing stopping power, the decrease of effective range is not a cause for concern. The only downfall is that if your firearm doesn’t cycle subsonic ammo you are going to be left with essentially a single shot to protect yourself with.

Subsonic rounds have their place, but aside from wanting or needing reduced noise and recoil, there is no reason to use them. Supersonic ammo is far superior to subsonic ammo in overall performance, stopping power, and effective range.