.450 Ackley Magnum

.458 Lott
.458 Lott, its parent case the .375 H&H Magnum and the .458 Winchester Magnum for comparison.
Type	Rifle
Place of origin	USA
Production history
Designer	Jack Lott
Designed	1971
Manufacturer	A-Square
Produced	1989
Variants	.458 Lott Improved, .450 Watts Magnum, .450 Ackley Magnum
Specifications
Parent case	.375 H&H Magnum
Case type	Straight, belted
Bullet diameter	.458 in (11.6 mm)
Neck diameter	.481 in (12.2 mm)
Base diameter	.513 in (13.0 mm)
Rim diameter	.532 in (13.5 mm)
Rim thickness	.050 in (1.3 mm)
Case length	2.800 in (71.1 mm)
Case capacity	110 gr H2O (7.1 cm3)
Rifling twist	1 in 14
Primer type	Large Rifle (Magnum)
Maximum pressure	62,500 psi (431 MPa)
Ballistic performance
Bullet mass/type Velocity Energy 300 gr (19 g) Barnes X 2,700 ft/s (820 m/s) 4,855 ft·lbf (6,582 J) 350 gr (23 g) Barnes X 2,600 ft/s (790 m/s) 5,252 ft·lbf (7,121 J) 400 gr (26 g) Barnes X 2,550 ft/s (780 m/s) 5,774 ft·lbf (7,828 J) 450 gr (29 g) Barnes Solid 2,450 ft/s (750 m/s) 5,996 ft·lbf (8,129 J) 500 gr (32 g) Barnes Solid 2,300 ft/s (700 m/s) 5,872 ft·lbf (7,961 J)

The .458 Lott is a .458 caliber belted hunting cartridge designed as a replacement for the less powerful .458 Winchester Magnum. It is based on the full length .375 H&H Magnum blown out and shortened to 2.800 inches (71.1 mm). The cartridge is designed for the purpose of hunting African dangerous game.

The .458 Lott was designed in response to perceived inadequacies and problems encountered with the .458 Winchester Magnum. While the cartridge was slow to gain popularity at first, it is now becoming the standard by which dangerous game cartridges are judged. The cartridge provides a distinct step up in performance over the .458 Winchester Magnum. A-Square, Česká Zbrojovka/Brno, Hornady and Ruger have been instrumental in the cartridge's rise in popularity.

The .458 Winchester Magnum was put into production in 1956 and was an immediate commercial success. It was a more economical alternative to the English double rifles that were considered the standard rifle type for dangerous game hunting in Africa. The .458 Winchester Magnum promised to emulate the performance of the .450 Nitro Express in a cartridge designed for a standard-length bolt-action rifle. However, it soon became apparent that the .458 Winchester Magnum was not performing as anticipated. Several factors contributing to its less than stellar performance in Africa: clumping of its compressed powder charge and use in 20–22 in (510–560 mm) barrel rifles.

Jack Lott, a big-game hunter and writer, had an adverse encounter in Mozambique in 1959 with an African Cape buffalo in which he sustained injuries. He had been hunting with the then new .458 Winchester Magnum. This experience convinced him that a more powerful cartridge than the .458 Winchester Magnum was required when hunting dangerous game. After the encounter he began a search for a big-bore cartridge which would suit his needs perfectly.