Centerfire cases being filled with Hodgdon Trail Boss powder.
Good Pour: Filling centerfire cases with Hodgdon Trail Boss powder. Joseph von Benedikt

You know the subsonic rimfire rounds so useful for quietly knocking off a varmint in the squash patch? Well, you can roll your own centerfire ammo that’s almost as quiet. And not just for your .300 Blackout AR. You can make subsonic loads for any of your favorite centerfire hunting rifles and use them to take varmints, predators, and even hogs and deer. There is a trick to it, though.

With common gunpowder, it’s generally not safe to underload high-power centerfire cartridges like the .270 or .308 so much that their projectiles move slower than the speed of sound. You need to use something else: namely, Hodgdon Trail Boss. Introduced just over a decade ago for cowboy-action shooters who wanted to shoot really light handloads, Trail Boss is an extremely bulky powder, which lets you fill an equal space with a smaller charge. For years, it has worked perfectly for loading revolver cartridge cases to full capacity for safe, light-recoil reloads. Now, with noise reduction in vogue, savvy handloaders are learning that it works just as well in centerfire rifle cases.

Trail Boss powder is so bulky that you can safely fill an empty centerfire case to the neck-shoulder junction, top that charged case with a bullet of correct diameter, and go try it out. Even with a case full of Trail Boss, the bullet won’t break the sound barrier, and you’ll be amazed at how stealthy your favorite deer rifle suddenly becomes.

Tamer Gamer

The main benefit of subsonic centerfire rounds 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.

Magic Bullet

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 burn more complete 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 ever.

Tip of the Month: Pick a Bone

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.