Subsonic Ammunition

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Before thinking subsonic ammunition is a logical addition for your new suppressor please take a minute to read this information below. Its not quite as simple and straightforward as Hollywood makes it seem.

The following article was copied from Field and Stream,

The label on the ammo box says subsonic, so this stuff won’t spook every deer in the county like your earth-shattering aught-six does, right? Well, sort of. Subsonic cartridges do produce less noise than full-velocity rounds, but there’s no free lunch—as usual. Your rifle will still go bang, and none of this quieter ammo is powerful enough for hunting big game much past slingshot range. Still, subsonic ammo does fill an important niche for many hunters and shooters.

What is Subsonic Ammo?

At sea level, the speed of sound is roughly 1127 feet per second. When a moving object, such as a bullet, breaks that threshold, there is an audible shock wave that sounds like the crack of a bullwhip. Most of the noise inherent with shooting a rifle, however, comes not from the bullet breaking the sound barrier, but from expanding gases rapidly escaping the rifle’s bore. It’s the latter bang that causes hearing damage, reveals shooters’ positions, scares game, and works Mrs. Walney down the road into a fit of agita. So while subsonic ammo does eliminate the downrange crack, and does reduce the bang at the muzzle somewhat due to its lower velocity, it won’t make your centerfire rifle sound like mouse feet on felt. It’s just one way to mitigate the noise.

Another way is to buy a silencer (legal in 39 states), which will greatly muffle those escaping gases. Quietest of all is to use a silencer in tandem with subsonic ammunition, which can reduce the sound of gunfire to a whimper in the rain. But if all we wanted was quiet, we wouldn’t pull the trigger at all. There’s still the question of performance, which is significantly hampered by going subsonic.

Is Subsonic Ammo Powerful Enough to Take Big Game?

Since energy is the product of mass times velocity squared, a slower bullet has exponentially less energy than a faster one of the same weight. Take your average 55-grain .223 Rem. bullet. At 3250 fps, it produces 1,280 foot-pounds of energy at the muzzle. But if you reduce the velocity to a subsonic 1100 fps, it produces only 150 foot-pounds. In other words, it turns a .223 Rem. into a .22 LR—the difference between a load for deer and a load for prairie dogs.

. This is one reason why you rarely see subsonic .223 loads on shelves. The other is because a lack of energy going forward equals a lack of energy going backward—and so they can fail to cycle semiautomatics.

To compensate for less velocity, you need more mass. That’s why rounds with long, large-­diameter bullets like the .300 AAC Blackout (which function well in modern sporting arms with a simple upper receiver swap) have become the preferred subsonic centerfire round for sportsmen, as well as for the military and law enforcement. It should be noted that these long bullets are most accurate when fired from barrels with fast 1:7 twist rates to stabilize them at subsonic speeds.

The Best Uses for Subsonic Ammo

The main benefit of subsonic centerfire rounds, when combined with a suppressor, is obvious enough: They’re quiet, making them ideal for suburban deer hunting, for discreetly trimming wild hog populations, or for quietly knocking back the coyote numbers.

on your deer lease. Granted, these loads have a maximum effective killing range of about 100 yards, but most whitetails and hogs are taken inside that distance. A less obvious benefit of these loads is reduced recoil. When you push bullets more slowly, they don’t push back so hard, making them perfect for practicing with heavy-kicking guns or for getting young hunters started with a big-game centerfire rifle.

How to Choose the Right Projectile for a Subsonic Load

Only one fly plagues the quiet-ammo ointment: Projectile choice for subsonic game loads is limited. Bullet expansion is critical for quick kills, especially on larger animals like deer and hogs. Most deer bullets won’t expand when fired at 1100 fps or slower. Traditional round- and flat-nose bullets with a lot of lead exposed at the tip do O.K., but the best of the lot are Hornady’s FTX bullets. Available in .25, .30, .32, .338, .35, and .458 caliber, they are engineered for vintage lever-action cartridges and expand reliably at very slow velocities.

In any case, use a bullet with a crimping groove. Because of the fluffy nature of Trail Boss powder, ignition is more consistent and propellant burns more completely with a crimp.

As a general rule, heavy-for-caliber bullets work best because they do a better job of retaining a subsonic round’s reduced energy downrange. However, if your rifling twist rate doesn’t spin bullets fast enough at subsonic speeds to stabilize long, heavy bullets, you’ll get better precision with lighter projectiles. If that’s the case, experiment until you find the heaviest bullet that shoots well. Also, subsonic rifle ammo probably won’t cycle your AR-15, Browning BAR, M1A, or other centerfire semiautomatic rifles. Not to worry—just run them like a straight-pull bolt action.

Finally, bullet trajectory will be vastly different with subsonic ammunition, so be sure and check your zero and test the point of impact out to 100 yards or so. Once that’s done, you’re ready to pop pigs, predators, and deer with more stealth than eve.

Adjust Shot Placement When Hunting with Subsonic Ammo

Because of the low impact velocity of subsonic bullets, they often don’t expand dramatically on game. Changing your shot placement to contact bone can help. Aim at the shoulder, halfway up the body or a shade more, to hit the scapula, which will aid bullet expansion. You’ll destroy both lungs, and meat damage will still be minimal because of the modest impact speed. This shot also allows room for error: Miss a little high and you’ll clip the spine, low and you’ll heart-shoot your deer.

This information above was adapted from Field and Stream and was written by Jeff Johnston. https://www.fieldandstream.com/guns/the-pros-and-cons-of-subsonic-cartridges

FAQ’s about Subsonic Ammunition

Is my rifle ready for subsonic ammunition?

Maybe, But not necessarily. The most important question to answer is what is your rifle twist rate? This dictates how many rpm the projectile will achieve and whether it will stabilize properly without tumbling. A modern factory rifle will most likely have a twist rate to slow to stabilize projectiles. You need a fast twist barrel to get enough RPM. Before you rush out and build a rifle just for shooting subsonic, please know that a fast twist barrel will overspin super sonic ammunitions.

Does Barrel Length Matter?

Yes, it’s extremely important. Velocity is created by building pressure behind your projectile. Longer barrels keep that pressure contained longer, therefore creating higher velocities. So say you load ammo to 1100fps in your 16″ barrel and then shoot it in your 22″, 24″, or 26″ you’re going to build more pressure, increase the velocity, and no longer have subsonic ammunition

Will I need to adjust my rifle to shoot subsonic ammunition?

Yes, you will need to zero your scope for your ammunition and a change your zero if you switch back to supersonic ammunition. This is know as Point of Aim Vs. Point of Impact. For example. A 308 Winchester shooting a 208gr Hornady ELD-M at 2500fps will drop 4″ or so from 100-200 yards. However, if you shoot the same projectile subsonic at 1050fps you will drop 33″ from 100-200 yards. This means you will shoot “Low” on the target if you put subsonic ammunition through your rifle with a 100yd zero for supersonic ammunition. So you will need to adjust your scope to accommodate for these differences.

Does Copper Creek make subsonic ammunition?

Yes, We can make subsonic in most cartridges, however please read and consider all the information above and after this period. You’ll need to know your rifle twist and length of your rifle barrel for starters. Check your manufacturers website for your twist rate if you don’t know it already. If your manufacturer does not explicitly state the rifle is for subsonic ammunition, it most likely won’t stand chance of stabilizing subsonic ammunition. You can contact us for a custom ammunition quote here: