Going Subsonic

I don’t find the subsonic approach particularly appealing, even while hunting nighttime feral hogs with thermal-equipped and suppressed ARs. I seem to be in the minority on this subject. Sure, subsonic is quiet, especially with a suppressed rifle. That holds obvious appeal. The sharp-stick truth is subsonic velocities sacrifice significant delivered energy and result in looping trajectories beyond 100 yards. Blame this attitude on being a child of the West, where 100 yards is considered rock-throwing distance, and success frequently hinges on the ability to go long. I’m rarely shooting where gunshots would annoy anyone.  

That said, I do understand the need in thronged Eastern woodlands. I use thronged to describe both the habitat and abundance of humanity and their myriad infrastructure. These are habitats where success typically comes after climbing into an elevated treestand or slumping onto a stump, resulting in average shot distances in the double digits. Intimate yardage largely solves the energy problem, the primary concern in the subsonic realm. 

When considering subsonic, the 300 Blackout is sure to enter the conversation or the new 338 ARC. Yet you likely already own a viable option in arguably North America’s two most popular big-game cartridges: the 308 Winchester and 30-06 Springfield. Most 308 Win and 30-06 owners I guided back in the day shot 180-grain factory loads. When fired from the 308 Win at around 2,500

feet per second (fps), such bullets produce nearly 2,500 foot-pounds (ft-lbs) of kinetic energy off the muzzle and 1,500 ft-lbs out to about 350 yards. The same bullet fired from a 30-06 at around 2,700 fps produces about 2,900 ft-lbs of kinetic energy off the muzzle and 1,500 ft-lbs out to around 425 yards. 

By contrast, subsonic loads with the same bullet produce little more than 450 ft-lbs of kinetic energy at the muzzle.

Bear with me if you’ve already heard this one, but subsonic loads means the bullets leaving the muzzle at less than the speed of sound, or Mach 1. Sound travels at 1,125.33 fps at sea level and 59 degrees Fahrenheit. Any bullets leaving the muzzle at higher velocities break the sound barrier and produce a distinctive crack. Temperature, air density/altitude and relative humidity all affect actual subsonic velocities. Ideally, when loading subsonic loads, you’d like to hit 1,100 fps under the atmospheric conditions most encountered, but most commercial subsonic loads are held to 1,050 to 1,080 fps to provide a buffer for the disparate conditions customers are likely to encounter.  

Sending bullets at less than the speed of sound is easy enough with the right powders (faster than usual for individual cartridges) and bullets (typically at the heavier end of the spectrum). But as the saying goes, speed kills. Subsonic loads are intentionally lacking in speed to remain beneath the sound barrier. The kinetic energy formula uses the weight of the projectile multiplied by velocity squared (divided by the constant 450,240). Velocity weighs heavily in the kinetic energy formula. When speed is reduced, kinetic energy suffers. I stress this only because hitting a deer with subsonic loads at 200 or 300 yards includes manageable drop margins from the 308 Win and 30-06 cartridges and bullets selected. Yet, that bullet just isn’t going to retain enough energy to ensure clean kills at such ranges. If you’re going to go subsonic, you’re also going to have to keep shots intimate.

Besides energy, there’s another important reason to keep ranges short. I normally consider 500 to 750 ft-lbs of energy the bare minimum for big game: the former for smaller deer and average-sized hogs, the latter for beefier deer or black bear. At subsonic velocities, the average .308-caliber big game bullet will expand minimally, though penetration shouldn’t pose problems. Still, I’ve spent enough time hunting with northern Innuits who gather winter meat with a 22 Winchester Magnum, or former African poachers who once killed an elephant with a 7.62x39mm Soviet, to understand shot placement is key. Close shots allow placing shots just so. 

The 308 Winchester test rifle was the new Balikli BLK distributed by EAA (European American Armory) Corp. This is a handsome Turkish-made bolt-action rifle featuring a beautiful walnut stock and a 20-inch barrel with an advertised 1:10 rifling twist and threaded muzzle. Given the subject matter, it proved ideal for this project. A Meopta Optika5 MeoPro 2-10x 42mm PA scope was set in Warne rings, creating an optimal pairing. I plan to conduct a full evaluation in the upcoming issue of Rifle & Handguns Magazine (No. 350, January 2027), so I don’t want to give too much away here, other than to say it provides a lot of rifle for the money.   

My classic Winchester Model 70 30-06 Springfield was also used for testing. It is truly representative of the type of hunting rifle so many whitetail hunters own. It was manufactured in 1966 and sports a 22-inch medium-contour barrel with 1:10 rifling twist. Traditionally, this hunting rifle has assembled 1-MOA or slightly smaller groups with tailored handloads, so I was curious to see how it would handle heavy bullets sent at a snail’s pace. It has held a sleek Tract TORIC HD 2-10x 44mm scope for many years, an optic well suited to Western mountain hunting or Eastern treestand approaches. It holds a BDC-style reticle and quality SCHOTE glass that provides clean, sharp viewing. 

The quest for subsonic loads limits handloaders to a handful of powders. Undoubtedly, other powders than those selected will serve, but the listed options include proven track records. These include faster-burning pistol or straight-walled cartridge powders such as Hodgdon Titegroup, Hodgdon Trail Boss, Accurate 5744 and Shooters World Buffalo Rifle. Low doses of medium-fast burn-rate rifle powders also work well, including Hodgdon 4895, H-322 and Benchmark. Two different loads were auditioned with each powder to increase the odds of hitting the subsonic mark with the test rifle’s 20- and 22-inch barrels. It was also hoped this would provide data points for fps gained or lost per 1/10-grain of powder, which didn’t exactly work out.  

Case/chamber dynamics obviously influence powder charges. The 308 uses 1 to 2 grains less Hodgdon 4895, Trail Boss, H-322, Titegroup and Benchmark to hit the subsonic mark than the 30-06. With high-density

Accurate 5744, the 308 requires about a grain more powder than the 30-06 to produce subsonic velocities. Also, as bullet weights increase, slightly more powder is added to produce identical subsonic velocities. In general, any time you drop substantially below the powder charges listed, do so with caution, while watching for squib loads. What was left to be seen was how barrel length would affect final velocities, as Hodgdon’s data developed with a 24-inch tube.    

Once-fired Federal Cartridge brass was used in the 308 Win, and Remington brass in the 30-06. Federal Champion No. 210 Large Rifle primers were utilized for both. For dies, the 308 Win was loaded with Hornady Custom Grade New Dimension full-length dies, and the 30-06 with a Redding Full Length Die Set. 

A beam scale and powder trickler manufactured by RCBS were also employed.    

For bullets, I started with five examples weighing between 180 and 200 grains. The .308-caliber bullets kept on hand in this weight class are bonded-core or monolithic copper designs intended for elk or larger African plains game, which means they are unlikely to expand well at subsonic velocities. With that in mind, I initially chose Nosler’s 180-grain Ballistic Tip Hunting, a pair of 185-grain Northern Precision Saber Star hollowpoints (roundnose in the 308 Win and spitzer in the 30-06), Hornady’s 190-grain subsonic-optimized SUB-X and a 200-grain Quality Cartridge monolithic copper Game-StopR. With the Nosler, I surmised it would act as a controlled-expansion design at subsonic velocities, while I hoped the long-for-caliber copper bullet would tumble through vitals following impact. Ultimately, the Nosler and Quality Cartridge bullets were eliminated due to insufficient stabilization, particularly from the 308 Winchester. This illustrates the caution that loads should be tested thoroughly before introducing a suppressor to avoid the possibility of destroying a valuable accessory.  

Hornady’s 180-grain InterLock softpoint flatbase replaced the Nosler. This second range session also allowed adjusting original loads while seeking subsonic velocities, which proved successful. This is a classic bullet with a flatbase and internal InterLock ring that checks expansion. Its .425 G1 ballistic coefficient (BC) means it retains only 396 to 428 ft-lbs of kinetic energy at 100 yards after leaving the muzzle at 1,050 and 1,100 fps, respectively. It was set up with Hodgdon 4895 and H-322, and Shooters World Buffalo Rifle, in the 308 Win; Hodgdon 4895 and Trail Boss, and Shooters World Buffalo Rifle, in the 30-06. 

Pondering the question of bullet expansion, I contacted Bill Noody, owner of Northern Precision Bullets. Northern Precision’s custom abilities allow Noody to control all construction factors. While Northern Precision is renowned for bonded-core, high-weight-retention big-game options, I needed something quite the opposite. Noody created a pair of thin-skinned, non-bonded bullets holding his trademark Sabre Star hollow points and rebated boat-tails. The Sabre Star treatment is normally applied to Northern Precision defensive handgun bullets to maximize expansion and vital tissue damage from stubby barrels. These bullets would also prove ideal 300 Blackout fodder. 

The two 185-grain Northern Precision bullets, with their rebated boat-tail, should retain roughly the same kinetic energy as the slightly heavier Hornady. The roundnose was paired with the 308 Win and Accurate 5744, Hodgdon Titegroup and Benchmark; the 30-06 with the spitzer and Hodgdon 322, Benchmark and Trail Boss. 

Hornady’s 190-grain SUB-X was designed specifically for the 300 Blackout. Long grooves in the jacket, its flat profile, and patented Flex Tip insert inside the deep hollowpoint cavity were designed to initiate reliable expansion at subsonic velocities. With its .437 G1 BC, it retains 419 and 453 ft-lbs of energy at 100 yards when sent at 1,050 and 1,100 fps. Powder choices included Hodgdon 322, Trail Boss and H-4895 in the 308 Win, and Accurate 5744, Hodgdon 322 and H-4895 from the 30-06.    

The quest for subsonic velocities produced some interesting anomalies. The biggest surprise was discovering that adding a few tenths of a grain of powder often resulted in slower velocities in the loads tested. This I cannot explain, other than that with charges so small, standard deviations might account for the discrepancies. That said, extreme velocity spreads remained remarkably low considering the light charges. 

The shorter barrel lengths also tossed some monkey wrenches into the equation. With the 308 Win’s 20-inch barrel, in particular, hitting the subsonic mark will require less powder with a majority of the powders tested. The tested loads resulted in several sub-MOA groups from the 308 Win firing Hornady’s InterLock, the Northern Precision roundnose Sabre Star hollowpoint (which presented some feeding issues) and Hornady SUB-X. The adjusted InterLock loads all hit the subsonic mark, while only two of the SUB-X loads met our goals.  

Things improved markedly with the Winchester M70 30-06 and its 22-inch barrel. Hornady’s 180-grain InterLock did not shoot as well in the 30-06, its best showing measuring 1.26 inches at 1,118 fps. The Northern Precision Sabre Star spitzer hollowpoint boat-tail produced two excellent groups – one at a pokey 949 fps, another at a marginally supersonic 1,346 fps. The Hornady SUB-X worked out best in the 30-06, producing two true subsonic loads with sub-MOA and sub-1⁄2-MOA groups. The clear winner from my rifle was .43-inch at 1,080 fps using 14.7 grains of Hodgdon 4895. 

Hodgdon 4895 and H-322 came the closest to matching the velocities of Hodgdon’s data for the 190-grain Hornady SUB-X in the 20- and 24-inch barrels. The fastest-burning powders gave the largest discrepancies (much higher velocities) in loads not adjusted for the 180-grain Hornady. These included Hodgdon Trail Boss, Accurate 5744 and Titegroup pistol powders, in particular. Buffalo Rifle loads hit the mark with the 308, but came up well short from the 30-06. This project reminded me yet again that developing subsonic loads for a particular rifle requires some careful load-ladder trial and error. Yet even those loads that didn’t hit the desired mark provide safe starting points for developing your own subsonic ammunition suitable for close-range whitetail or hog hunting in settled areas.