Holland and Holland, a British company, introduced the .300 H&H Magnum in 1925. Initially called the “Super-Thirty,” it was designed to hunt African plains animals. The .300 H&H Magnum will harvest all African game animals except the very largest. The .300 H&H Magnum has been successfully employed for elk hunting, as well as taking moose and other large game animals in North America. Popular not only among hunters, competitive target shooters have used the .300 H&H Magnum successfully with the first major victory taking place in 1935 at the Wimbledon Cup; Ben Comfort was the shooter. This win exposed the cartridge to hunters and target shooters alike. Winchester released the Model 70 in 1937 chambered for the .300 H&H Magnum, and in the process, cemented the cartridge as a global leader for years to come of high performance magnum cartridges.
Bullet weights for the cartridge are available between 150 grains and 220 grains. Muzzle energy for the .300 H&H Magnum can exceed 3,700 foot pounds, and muzzle velocities can exceed 3,300 feet per second. The case for the .300 H&H& Mag is based on Holland and Holland's most popular cartridge, their .375 H&H Magnum. They necked down the case of the .375 to accept a 0.309" bullet. The case is belted and has a narrow sloping shoulder. It is unusual to see a narrow shoulder like this, but the .300 H&H Magnum has proven to have superior ballistics to the .30-06. The hunting public took notice of these numbers. An area where the .300 H&H Magnum capitalizes on its heavy bullet moving fast, in addition to its high ballistic coefficient, is at ranges beyond 200 yards. Even as far as 400 yards out, the .300 H&H retains about 2,000 foot pounds of energy.
When the .300 Winchester Magnum was introduced in the 1960's, the .300 H&H Magnum declined in popularity. Some voices of the gun culture speculated that only the fine double barreled rifles which H&H made were what kept the cartridge alive. The cartridge has experienced a new growth in popularity over the past few years, likely due to manufacturers selling bullets on the leading edge of ballistic technology. Federal, for example, sells Nosler Partition bullets and Barnes Triple-Shock bullets in the .300 H&H Magnum cartridges they manufacture.