.300 Winchester Magnum

.300 Winchester Magnum
.300 Winchester Magnum (center) flanked by its parent cartridges: the .338 Winchester Magnum (left) and the .375 H&H Magnum (right).
Type	Rifle, Large game
Place of origin	United States
Production history
Designer	Winchester Repeating Arms Company
Designed	1963
Specifications
Parent case	.375 H&H Magnum
Case type	Belted, bottleneck
Bullet diameter	.308 in (7.8 mm)
Land diameter	.300 in (7.6 mm)
Neck diameter	.339 in (8.6 mm)
Shoulder diameter	.489 in (12.4 mm)
Base diameter	.513 in (13.0 mm)
Rim diameter	.532 in (13.5 mm)
Rim thickness	.050 in (1.3 mm)
Case length	2.62 in (67 mm)
Overall length	3.34 in (85 mm)
Case capacity	94 gr H2O (6.1 cm3)
Rifling twist	1 in 10 in (250 mm)
Primer type	Large Rifle Magnum
Maximum pressure (C.I.P.)	62,366 psi (430.00 MPa)
Maximum pressure (SAAMI)	64,000 psi (440 MPa)
Maximum CUP	54,000 CUP
Ballistic performance
Bullet mass/type Velocity Energy 150 gr (9.7 g) GMX 3,300 ft/s (1,000 m/s) 3,628 ft⋅lbf (4,919 J) 180 gr (11.7 g) BT 3,193 ft/s (973 m/s) 4,076 ft⋅lbf (5,526 J) 190 gr (12.3 g) BTSP 3,117 ft/s (950 m/s) 4,100 ft⋅lbf (5,600 J) 200 gr (13.0 g) Partition 3,029 ft/s (923 m/s) 4,092 ft⋅lbf (5,548 J) 220 gr (14.3 g) Sierra MatchKing (HPBT) 2,875 ft/s (876 m/s) 4,038 ft⋅lbf (5,475 J)
Test barrel length: 24 inches (61 cm) Source(s): Accurate Powders load guide v3.5[1] Hodgdon powders achieve approx 100fps less.[2]

The .300 Winchester Magnum (also known as .300 Win Mag or .300 WM) (7.62×67mmB, 7.62x66BR) is a belted, bottlenecked magnum rifle cartridge that was introduced by the Winchester Repeating Arms Company in 1963. The .300 Winchester Magnum is a magnum cartridge designed to fit in a standard rifle action. It is based on the .375 H&H Magnum, which has been blown out, shortened, and necked down to accept a .30 caliber (7.62 mm) bullet.^[3]

The .300 Win Mag is extremely versatile and has been adopted by a wide range of users including big game hunters, target shooters, military units, and law enforcement departments.

Many hunters have found the cartridge to be an effective all-around choice with bullet options ranging from the flatter shooting 150 grain to the harder-hitting 200+ grain selections available in factory ammunition. The .300 Win Mag remains the most popular .30 caliber magnum with American hunters, despite being not being as fast as more powerful .300 Magnums such as the .300 Weatherby Magnum and .30-378 Weatherby Magnum as well as the newer .300 Remington Ultra Magnum, .300 Norma Magnum, .30 Nosler, and .300 PRC, though all of these must be chambered in a long magnum action while the .300 Win Mag uses a standard length action, resulting in a lighter rifle.^[4]

It was designed as a hunting cartridge and is widely used all over the world for hunting a wide range of mid-to-large-sized big game such as North American moose, elk, bighorn sheep, mule deer and white-tailed deer, making it one of the most versatile big game hunting cartridges.

The .300 Win Mag is capable of delivering better long-range performance with heavier, large ballistic coefficient projectiles than any other standard and short length .30 caliber cartridge. Military and law enforcement departments have also adopted the cartridge as a long-range sniper round, intended to be used for shots at longer ranges than the .308 Winchester. As a testament to its accuracy, following its introduction, it went on to win several 1,000-yard (910 m) competitions.^[5]