With suppressors being very popular, I wanted to post some information about SUBSONIC ammo and the differences between subs and super sonic ammo, and shooting suppressed. SUBSONIC, in terms of ammo, simply means the bullet is going below the speed of sound. The speed of sound is about 1110 fps, depending on your exact environmental conditions. To allow for some variables in barrel lengths and such, my subsonic ammo runs about 1000-1060 fps. When a bullet is going below the speed of sound, there is no sonic “crack” and the bullet has a very quiet flight. When a bullet goes above the speed of sound (about 1110 fps), the bullet will now have a sonic “crack”, just like the end of a cowboy’s bull whip. (The reason why a whip has a “crack”, is because the end of the whip breaks the sound barrier). A SUBSONIC round will have no sonic crack. When shooting this SUBSONIC round suppressed, the suppressor will muffle the bang, and the round will be very quiet. (See “Energy of a SUBSONIC” round below).
Energy of a SUBSONIC
To make a SUBSONIC round, the ammo is loaded to a much lower pressure to keep the bullet below the speed of sound, about 1000-1060 fps. With these slower speeds, the energy of the round has been heavily reduced. Take a SUBSONIC 308 Winchester with a 180 grain bullet going about 1040 fps. This round has about 430 ft lbs of energy at the muzzle, and about 380 ft. lbs. of energy at 100 yards. In comparison, a 40 S&W handgun round pushes the same weight 180 grain bullet about the same speed of 1040 fps as a 308 SUBSONIC round does. So, this 308 Win SUBSONIC round has almost the same energy as a 40 cal round, but fired out of a rifle platform. So, keep this energy level in mind. Also, at these slower speeds, the bullet will not have any expansion. With a standard bullet, the bullet will often, what I call ice pick through your target. The bullet has no expansion and minimal hydrostatic shock. A full power super sonic 308 Win round will have about 6.5 times the energy of a typical SUBSONIC round. So, keep this in mind when hunting with a subsonic round.
SUPPRESSORS!!
A lot of shooters get a suppressor, and think that they now must shoot subsonic ammo. You can shoot any ammo you want that you would normally shoot, including full power super sonic ammo or subsonic ammo. Just keep in mind that when you add a suppressor you raise the pressure of the ammo you are shooting about ~3000-5000 psi. So if you are shooting a stiff load that’s near max pressure without a suppressor, adding the suppressor can easily increase your pressures to make it a warm or hot (i.e. unsafe) load.