The .950 JDJ (24.1×70mm) is a powerful large caliber rifle cartridge developed by American gunsmith and weapon designer

J. D. Jones J. D. Jones (born November 21, 1936) is an American firearms and cartridge designer, firearms writer and president of SSK Industries. Jones began hunting at an early age, and became interested in bullet casting and handloading firearms cartri ...

of SSK Industries.

Cartridge

.950 JDJ cases are approximately 70 mm in length, and are based on a

20×110mm 20 mm caliber is a specific size of popular autocannon ammunition. It is typically used to distinguish smaller-caliber weapons, commonly called "guns", from larger-caliber "cannons" (e.g. machine gun vs. autocannon). All 20 mm cartridges ...

case shortened and necked up to accept the bullet. Projectiles are custom-made and most commonly weigh which is 8.2

ounces The ounce () is any of several different units of mass, weight or volume and is derived almost unchanged from the , an Ancient Roman unit of measurement. The avoirdupois ounce (exactly ) is avoirdupois pound; this is the United States customa ...

or over half a pound.

Rifles

As its name implies, rifles chambered for the cartridge have a groove diameter of . SSK received a "Sporting Use Exception" to de-regulate the rifles. Thus, in the United States, they can be owned like any other Title I rifle by an American citizen at age 18. The rifles use

McMillan Firearms McMillan Firearms is an American arms manufacturer best known for the McMillan Tac-50, its .50 BMG long-range anti-materiel and sniper rifle. It also produces the McMillan Tac-338, McMillan Tac-300 and McMillan Tac-308 sniper rifles, the ALIAS R ...

stocks and extraordinarily thick Krieger barrels bearing an

muzzle brake A muzzle brake or recoil compensator is a device connected to, or a feature integral to the construction of, the muzzle or barrel of a firearm or cannon that is intended to redirect a portion of propellant gases to counter recoil and unwanted ...

. Overall, depending on options, the rifles weigh from and are therefore only useful for shooting from a bench rest or heavy bipod. Despite the weight, recoil is significant and shooters must be sure to choose components (i.e.,

scopes Scope or scopes may refer to: People with the surname * Jamie Scope (born 1986), English footballer * John T. Scopes (1900–1970), central figure in the Scopes Trial regarding the teaching of evolution Arts, media, and entertainment * CinemaS ...

and

bipod A bipod is a V-shaped portable attachment that helps support and steady a device, usually a weapon such as a long gun or a mortar. The term comes from the Latin prefix ''bi-'' and Greek root ''pod'', meaning "two" and "foot" respectively. Bipod ...

s) that can handle the force. The sheer size, weight, and power of these rifles make them rather impractical for hunting use. SSK only manufactured three of these rifles and as of 2014 no longer produces the ammunition.

Ballistics

The cartridge propels its bullet at approximately . This yields a muzzle energy of . By comparison, the

5.56×45mm NATO The 5.56×45mm NATO (official NATO nomenclature 5.56 NATO, but often pronounced "five-five-six") is a rimless bottlenecked intermediate cartridge family developed in the late 1970s in Belgium by FN Herstal. It consists of the SS109, L110, and ...

cartridge, used in the

M16 The M16 rifle (officially designated Rifle, Caliber 5.56 mm, M16) is a family of military rifles adapted from the ArmaLite AR-15 rifle for the United States military. The original M16 rifle was a 5.56×45mm automatic rifle with a 20-roun ...

and M4 rifles, produces between , while the

.308 Winchester The .308 Winchester is a smokeless powder rimless bottlenecked rifle cartridge widely used for hunting, target shooting, police, military, and personal protection applications globally. It is similar but not identical to the 7.62×51mm NATO ...

, a favorite for hunters, police, and military sniping, produces between depending on the load used. Even the .50 BMG, which has a kinetic energy of around delivers less than half the energy. The ballistics of the .950 JDJ are more similar to that of the 20 mm autocannon round, which delivers approximately . The muzzle energy of the .950 JDJ is comparable to the kinetic energy of a automobile traveling at . In a rifle, this will develop well over of

free recoil Free recoil is a vernacular term or jargon for recoil energy of a firearm not supported from behind. Free recoil denotes the translational kinetic energy (''Et'') imparted to the shooter of a small arm when discharged and is expressed in joules ( ...

energy. Shooting usually involves a heavy "lead sled" or similar shooting rest, and the rifle scope has significant eye relief to avoid injuring the ocular orbit.

References

{{DEFAULTSORT:950 JDJ Pistol and rifle cartridges Large-caliber cartridges JDJ cartridges