.500 Linebaugh

The .500 Linebaugh (13x35mmR) is a .50 caliber handgun cartridge designed for use in handguns. It is considered one of the most powerful handgun cartridges designed in terms of kinetic energy and power factor (momentum).

History
Inspired by the existing .50 WT Super cartridge devised by Neil Wheeler and Bill Topping of Sandy, Utah, John Linebaugh developed the .500 Linebaugh cartridge in 1986. Linebaugh was then known for converting six-shot .45 Colt revolvers to five-shot configuration, which allowed the use of higher-pressure ammunition than would be safe in many existing firearms chambered for the cartridge. While this venture was a success, Linebaugh was intrigued by Wheeler and Tompin's work, and decided to pursue a .50 caliber handgun cartridge of his own.

The cartridge case itself was designed by cutting off the .348 Winchester case to 1.405 in, turning the rim to a diameter of .610 in and opening the case mouth to accept a .510 caliber (12.95 mm) bullet. The first revolvers converted to use the .500 Linebaugh were the Ruger Bisley and the Seville revolvers. Due to the demise of the Seville revolvers in the early 1990s, most subsequent conversions have been carried out on revolvers based on the Ruger Bisley frame.

It was when the supply of .348 Winchester cases started running out that John Linebaugh began working on the .475 Linebaugh, which could be formed from the more available .45-70 Government cases. When the Winchester Model 71 was reintroduced in the .348 Winchester, the ability to form .500 Linebaugh cases again became feasible. Today, Starline and Buffalo Bore offer .500 Linebaugh cases which are not dependent on the supply of .348 Winchester cases.

Cartridge design and specifications
The .500 Linebaugh is a proprietary cartridge and thus has not been adopted by mainline firearms manufacturers. Currently the only firearm manufacturer that produces a revolver for this cartridge is Magnum Research (owned by Kahr Firearms Group), in the BFR product line. Prior to January 2019, the only alternative was to have a gunsmith such as John Linebaugh of Linebaugh Custom Six guns or Hamilton Bowen of Bowen Classic Arms convert pre-existing revolvers such as the Ruger Blackhawk and Bisley to fire the cartridge. Bowen is known to have converted the Ruger Redhawk double-action revolver for use with this cartridge.


 * [[Image:500Linebaugh01.png|400px|alt=.500 Linebaugh Cartridge Schematic|.500 Linebaugh SAAMI cartridge - all dimensions in inches (mm)]]

Due to the proprietary status of the cartridge neither the CIP nor SAAMI have published official specifications for the cartridge. As is the case, there can be some variations from gunsmith to gunsmith. No pressure standard has been published for the cartridge but according to Linebaugh, pressure levels between 30000 psi and 35000 psi are considered safe in the converted revolvers.

The cartridge uses .510 in (12.95 mm) diameter jacketed bullets or .511-.512 in (12.98-13.01 mm) lead bullets.

Sporting usage
The .500 Linebaugh was designed as a hunting cartridge. It was designed to fire a 440 gr bullet at 1300 ft/s. This particular loading generates 1650 ftlbf of energy making this one of the most powerful handgun cartridges put into production. In terms of energy, this is comparable to the .454 Casull cartridge. However, the .500 Linebaugh provides a larger diameter, heavier bullet with a greater sectional density than the .454 Casull. As a hunting cartridge it is capable of taking any North American game animals and most African game species.