Follow along as we handload for this .338 caliber subsonic round to run in an AR-platform rifle.
It seems like every time I turn on the television there’s a show on that’s headlining the porker plague that’s sweeping North America. There’s little doubt that wild hogs are hostile habitat wreckers. It’s become a no holds barred wildlife management fight, and it is quite accepted to remove the offending hogs by nearly any means. One of the popular methods is to hunt them at night. Night vision optics and suppressors are acceptable tools in many areas to reduce herd numbers.
Over the past few months, the .300 Blackout has gathered quite a bit of attention for throwing heavy, aerodynamic bullets at subsonic velocities. I’ve seen firsthand the effectiveness of these loads on game within their range limitations. My interest in the .300 AAC BLK goes back several years to the .300/.221 Fireball and .300 Whisper. I’m also familiar with the .338 Whisper, and its effectiveness on game. When I stumbled upon the .338 Spectre, I knew its ability to sling 300-grain Sierra Match Kings at subsonic velocities would have no trouble as a reliable close-range pig thumper.
Like the .458 SOCOM, the .338 Spectre cartridge was developed specifically for the AR-15 family of gas-operated, detachable-box magazine-fed firearms. The cartridge is intended to fill the gap between traditional pistol caliber cartridges and existing rifle cartridges used in this weapon system. It shares rim size with the new Remington 6.8 x 43mm SPC cartridge, allowing use of OEM bolts for this cartridge.
Works in Bolt Guns, too
By offering ballistics similar to the .357 Maximum, the .338 Spectre offers great potential as a single shot, silhouette and small game cartridge. By using .338 caliber bullets, the cartridge offers a nice variety in projectile choice, ranging from 160-grain Barnes X Spitzers, through 180-grain BST to 300-grain HPBT Match King rifle bullets. Furthermore, it allows the user to employ existing suppressors for the 9mm without modification.
The .338 Spectre cartridge is based on the Starline 10mm Magnum case. Overall loaded length is similar to the ubiquitous 7.62 x 39mm, .223 Remington, and bares a resemblance to the little-known 9x39mm cartridge chambered for the Russian Vintorez assault rifle.
Standard .223-caliber AR-15 magazines will accept a limited number of .338 Spectre cartridges, whereas the 7.62×39 magazines are fully compatible. Since the cartridge shares rim and head dimensions with the new 6.8 x 43 SPC, the preferred magazines are those made specifically for the 6.8 x 43 by PRI. The standard .223 lower receiver for an AR-15 needs no modification, and the rifle will function in both semi and full automatic modes. In addition to the AR-15 weapons platform, several other types of firearms can be made to accept this cartridge, including the Ruger Mini-14, T/C Encore and various bolt and pump action rifles.
Ballistic performance is comparable to the .357 Herrett, .35 Remington or even the 180-grain load for the .44 Magnum. In the 16-inch barrel carbine, the .338 Spectre will launch the 180-grain BT at 1,800 fps, approaching 1,300 ft-lbs. of energy. By loading the 300-grain Sierra HPBT Match King bullet at subsonic velocities (1,040 ft/sec.) for suppressed applications, the muzzle energy measures 720 ft-lbs., surpassing both the high velocity 115-grain load for the 9mm Parabellum as well as the 240-grain .300 Whisper load. For the sportsman, the .338 Spectre offers a user-friendly cartridge in terms of brass forming and reloading with light recoil and excellent performance on small to medium sized game. For the law enforcement professional, it offers solid terminal ballistics from one of the most-widely used weapons platforms with minor modification.
Teppo Jutsu Invented .338 Spectre
The leader in .338 Spectre development is Teppo Jutsu, a custom AR manufacturer. Developed by Teppo Jutsu owner, Marty ter Weeme, the cartridge uses as its parent case is the 10mm Magnum. It is possible to make .338 Spectre brass from 6.8 SPC brass with a lot of work, though.
When I got my hands on a 16-inch barreled .338 Spectre Teppo Jutsu and a set of dies, I was anxious to get started. Starline didn’t have any 10mm Magnum brass available at the time, so I spent the better part of three hours turning 30 6.8 SPC brass cases into Spectre brass.
Gun Specs
| Manufacturer | Teppo Jutsu LLC |
| CALIBER | .338 Spectre |
| BARREL | 16 inches, 1:6.5 twist |
| OA LENGTH | 41 inches |
| WEIGHT | 8 pounds, 14 ounces (empty) |
| SIGHTS | Vortex 0-4x Scope |
| STOCK | Vltor |
| ACTION | Semi-auto, piston |
| FINISH | Hard-anodized aluminum, Duracoat digital camo |
| CAPACITY | 5-, 10- and 25-round 6.8 SPC magazines |
To get started, I annealed the brass to reduce the number of ruined cases. Using a .308 Winchester resizing die, screwed the expander plug as far down as it would reach. This first pass expanded the neck, and made it easier to do the same step with a .338 Winchester Magnum expander die. The last expanding step was to take a 9mm Parabellum expander die and make the case nearly straight-walled. I screwed the .338 Spectre size die into my RCBS Rockchuker press with the expander removed to set the shoulder to create a dummy round.
Next, I ran the dummy case through Hornady’s Lock-N-Load Case Prep Center to cut the case to its proper length. After smoothing the case mouth, I screwed in a .338 Spectre bullet seating die and seated a 300-grain Sierra Match King. From this dummy round, I took measurements to find out how much case neck thickness would need to be removed to build a functional case.
An earlier discussion with ter Weeme that final neck diameter should be .361 maximum with a seated bullet, I measured with a micrometer to see how much to trim the oversized the case neck. Marking the cases to show the approximate location of the shoulder, I took the cases that had been opened up to .355 from the 9mm expander die and outside neck reamed to bring them back down in thickness. When finished reaming, I ran the cases through the .338 Spectre size die for a final forming. I loaded these cases twice over the following weeks and did some shooting. Thankfully, I won’t ever have to go through this laborious process, since the Starline 10mm Magnum brass finally arrived on my doorstep before I was forced to create more Spectre from 6.8 SPC brass.
Wanting to learn more about the penetration capabilities of the .338 Spectre, I used the old test medium of wet newspapers. Starting with 9.5 grains of IMR 4227 to push the 300-grain SMKs at an average of 885 fps, I increased this load until I topped 1,000 fps reliably without going over 1,080 fps. The average velocity for my final load averaged 1,022 fps. Firing into a stack of wet newspaper, the 300-grain SMKs averaged penetrating 18 inches, which is plenty to shoot through most hogs’ chest cavities. The load I used for the penetration test wasn’t a good load for accuracy, since it averaged putting 10-shot groups into 5.45 inches at 100 yards.
Accuracy improved when I switched powders. Reloader 7 did well when pushing 250-grain Sierra Match Kings and Hornady boat-tail hollow-point match bullets. My starting load of 14.5 grains of RL7 put 10 shots into 1.67 inches at 100 yards while shooting a 4x Vortex scope. The 20 fps standard deviation for this load was admirable, but the velocity averaged 1,201 fps, and would have been too fast to stay subsonic if shooting a suppressor. The same powder charge pushing a 250-grain Sierra Match King made me think that my chronograph wasn’t working, since it recorded a standard deviation of 165 fps for a 10-shot string. The average velocity of 1,017 fps made me question the usefulness of this for a subsonic load, but accuracy was fine. It averaged a tad over 1.9 inches for 10 shots at 100 yards.
Handloading isn’t the only option for shooting the .338 Spectre. After I was well under way with this project, I received a few rounds of ammo from Southern Ballistics Research (SBR). Currently they offer two loads with 250-grain spitzers; one load is subsonic from 12-inch barrels, while the other is listed at 1,520 fps. SBR also offers .338 Spectre head-stamped brass. (www.sbrammunition.com). The best 10-shot group I recorded measured 3.58 inches, again, at 100 yards with the 4x Vortex. I’m sure that my initial accuracy testing would shrink groups if fired with a higher-magnification optic.
At the beginning of my search for good handloads, I tried a Lee cast bullet weighing 220 grains. Regrettably, this subsonic load was a miserable failure. The Teppo Jutsu’s barrel has an incredibly fast 1:6.5-inch twist rate to stabilize long 250- to 300-grain jacketed bullets. The fast twist rate was just too much for the cast lead bullets to handle, and heavy barrel leading resulted. I would like to try a much slower twist-rate barrel for cast bullets some day, but until then I’ll have to settle for shooting much more expensive jacketed bullets for this cartridge and gun combo.
Under 200 yards, this caliber at subsonic velocities has taken many whitetails in my neck of the woods. And, if you are looking for a suppressor-ready subsonic AR that can deliver a heavy-weight slug at subsonic velocities for hunting, then you may want to take a hard look at the Teppo Jutsu .338 Spectre. It promises to become a real pig thumper.
| FACTORY LOAD | VELOCITY | ACCURACY |
| SBR Subsonic 250 | 1,200 +/- | 3.58 |
| HANDLOAD | Powder/Charge Weight | Accuracy |
| Sierra Match King/300 | IMR 4227 / 14.5 gr | 5.00 |
| Sierra Match King/250 | RE7 / 14.5 gr. | 1.67 |
| Hornady Match BTHP/250 | RE7 / 14.5 gr. | 1.81 |
Inspired by the 9x39mm Russian
The 9×39 mm is a Russian subsonic assault rifle cartridge based on the Russian 7.62×39 mm round, but with an enlarged neck to accommodate a 9mm bullet. The cartridge was designed by N. Zabelin, L. Dvoryaninova and Y. Frolov in the 1980s. Their intent was to create a subsonic cartridge for suppressed firearms for special forces units that had more power, range and penetration than handgun cartridges. The bullet of the 9×39 mm is approximately 250 grains, doubling that of the 7.62×39 mm, and is subsonic. The round has an effective lethal range of 300 to 400 meters and a maximum penetration of up to 10mm of steel. Like the 5.45x39mm cartridge, 9x39mm SP-5 features an air pocket in the tip, which vastly improves its capability to yaw. Yawing can be quite violent with this round.
The VSS (Vintovka Snayperskaya Spetsialnaya) or “Special Sniper Rifle,” also called the Vintorez, or “thread cutter,” is a silenced sniper rifle also developed in the late 1980s and manufactured by the Tula Arsenal. It is issued primarily to Spetsnaz units for covert operations, a role made evident by its strip-down capability for transporting in a specially fitted briefcase.
The overall operating principle and sound suppression system used on the VSS are derived from the AS assault rifle. The VSS is a gas-operated select-fire rifle. It has a long-stroke gas piston operating rod in a gas cylinder above the barrel. The VSS is striker fired, and features a cross-bolt type fire selector switch located behind the trigger, inside the trigger guard. The safety lever and the charging handle resembling those used in AK-style weapons.
The weapon has an integral suppressor that wraps around the barrel. The barrel itself has a series of small ports drilled in the rifling grooves, leading into the silencer which slows and cools the exhaust gases. The suppressor removes for storage or maintenance, but the VSS should not be fired without the suppressor.
The skeletonized wooden stock is a more rounded version of that provided on the SVD rifle; it has a rubber shoulder pad and can be removed when the rifle is dismantled for compact storage. The forward handguard is made from a high-impact polymer.
The VSS is normally fed from a 10-round magazine and fired semi-automatically. Should the operational need arise, the weapon can be used in fully automatic mode using 20-round magazines from the AS rifle.
It uses a heavy subsonic 9x39mm SP-5 cartridge. The bullet is very effective at penetrating body armor. For this purpose, it is equipped with a hardened steel or tungsten tip to penetrate a 0.2-inch high-density steel plate at 100 meters. A 0.08-inch steel plate army helmet can be fully penetrated at 500 meters. However, the rifle is typically employed under 400 meters.
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