.358 JDJ (Handloader issue #357)

The .358 JDJ is a powerful wildcat cartridge developed during the late 1970s by renowned handgun hunter and cartridge designer J.D. Jones of SSK Industries. Created by necking the .444 Marlin case down to accept .358-inch bullets, the cartridge was specifically engineered for use in the Thompson/Center Contender single-shot pistol. Jones sought to maximize the performance potential of the Contender action while maintaining safe operating pressures and efficient powder combustion in relatively short barrels. The result was a cartridge capable of delivering rifle-like energy from a hunting handgun, making it highly effective on deer, elk, black bear, and many other large game animals.

Unlike many wildcat cartridges developed solely for increased velocity, the .358 JDJ was designed with practical hunting performance in mind. The large-capacity case allows it to propel 180- to 250-grain bullets at impressive velocities, providing excellent penetration and reliable terminal performance. The cartridge quickly earned a reputation for outstanding accuracy and efficiency, particularly when chambered in 14- and 16-inch Contender barrels. Although it produces substantial recoil in handgun platforms, experienced hunters appreciated its ability to cleanly harvest game at distances previously considered unrealistic for specialty pistols.

Handloaders have played a central role in the continued popularity of the .358 JDJ. Since it has never been standardized as a commercial cartridge, ammunition is typically formed by resizing readily available .444 Marlin brass. The extensive selection of .358-inch bullets originally intended for cartridges such as the .35 Remington and .358 Winchester gives reloaders considerable flexibility, allowing loads to be tailored for everything from medium-sized game to the largest North American species. Modern powders and premium hunting bullets have further improved the cartridge's performance while maintaining excellent accuracy and case life.

Although newer specialty handgun cartridges have emerged over the years, the .358 JDJ remains one of J.D. Jones' most successful and respected designs. Its combination of power, accuracy, and efficient case design helped establish SSK Industries as a leader in specialty handgun hunting cartridges and demonstrated the remarkable capabilities of the Thompson/Center Contender platform. Today, the .358 JDJ continues to be valued by dedicated handloaders and handgun hunters who appreciate its proven field performance and enduring place in wildcat cartridge history.

Source: Handloader Issue #357 – August 2025