The .300 Winchester Magnum (also known as .300 Win Mag or .300 WM) (7.62×67mmB, 7.62×66BR) 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.Lyman Reloading Handbook, 48th Edition, 2002
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 among American hunters, despite faster and more powerful .300 Magnums options 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.
It was designed as a hunting cartridge and is mainly used 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.
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 competitions.
Cartridge history
Before the advent of the .300 Winchester Magnum, there were already many .30-caliber (7.62 mm) cartridges billed as offering a "magnum" level of performance. Such rounds included the .30 Newton of 1913 and the .300 H&H Magnum of 1925. The .30 Newton saw limited commercial success, however, and the .300 H&H was too long for the standard length Mauser and Springfield rifle actions of the time, barring substantial modifications.
Beginning with the .270 Weatherby Magnum in 1943, Roy Weatherby introduced a popular line of rifle cartridges based on the H&H case shortened to fit a standard length () action. The Weatherby cartridges of any given caliber followed an "improved" design that entailed "blowing out" the H&H Magnum parent case, thereby reducing case taper and increasing usable powder capacity. The .300 Weatherby Magnum, an "improved", full-length cartridge derived from the .300 H&H, was introduced in 1944.
The larger manufacturers soon noticed Weatherby's standard-length magnum case and, in due time, followed suit. From 1956 to 1959, Winchester introduced three such cartridges: the .264 Winchester Magnum, .338 Winchester Magnum and .458 Winchester Magnum, all based on the shortened and blown out .375 H&H Magnum case. The omission of the popular .30 caliber from that lineup prompted a response from the shooting community and Winchester's competitors. Wildcatters soon produced the .30-338 Winchester Magnum, and Norma Projektilfabrik, who were by now manufacturing ammunition for Weatherby, took the standard-length basic Weatherby brass and necked it down to .30 caliber (7.62 mm) to form the .308 Norma Magnum.
The .300 Winchester Magnum was introduced in 1963 by Winchester for use in the Model 70 rifle. Winchester developed the .300 Win Mag by taking the .338 Winchester Magnum, which was introduced in 1958, moving the shoulder forward by and lengthening it by . This resulted in a cartridge with a neck slightly shorter than the bullet's diameter. Some gun writers have speculated that, had the cartridge been released earlier, its dimensions would have more closely matched the .30-338 Winchester Magnum wildcat cartridge.
The .300 Winchester Magnum was not an instant success, mainly due to competition from the comparable 7mm Remington Magnum cartridge introduced in 1962. However, interest among hunters and shooters grew with time, and it gradually became the most popular of the magnum cartridges.
The .300 Winchester Magnum's broad availability in popular rifles such as the Winchester Model 70, Ruger M77, Remington Model 700 and Weatherby Mark V, together with the wide availability of ammunition from many manufacturers, made the cartridge a popular choice among hunters and competitive shooters the world over. Although the .300 H&H Magnum, .300 Weatherby Magnum, .30-338 Winchester Magnum, and the .308 Norma Magnum had a head start on the .300 Win Mag, most of these cartridges eventually faded into obscurity. Only the .300 Win Mag and the .300 Weatherby Mag survived into the 21st century as readily available cartridges, with the Winchester round by far the more popular of the two. New .30 caliber magnums have since been introduced, including the .300 Winchester Short Magnum, .300 Remington Ultra Magnum, .30 Nosler, and 300 PRC; however, none of these have achieved the popularity that the .300 Win Mag retains.
Design and specifications The .300 Winchester Magnum uses the same case head design as the .375 H&H Magnum, its parent cartridge, though the taper of the round has been significantly reduced to ensure greater case volume. The larger dimensions of the .300 Win Mag compared to the .308 Norma Magnum and .30-338 Winchester Magnum cartridges ensure that rifles chambered in such rounds can readily be rechambered to the .300 Win Mag. However, the longer rounds' shorter necks necessitate that comparable bullets be seated more deeply in the case.
Cartridge dimensions The ammunition standards organizations SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) and C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) have provided specifications for the .300 Winchester Magnum cartridge. Almost no divergence between C.I.P. and SAAMI dimensional values exists for this cartridge. However, case volume varies across manufacturers to such an extent that the reloading software suite QuickLOAD provides five distinct cartridge case capacities. The SAAMI specification .300 Winchester Magnum case capacity is 91.5 grains of H2O (5.93 ml). According to QuickLoad, the case capacities of .300 Win Mag brass produced by four ammunition manufacturers measure as follows: Remington 88.0 grains of H2O (5.70 ml) Federal 92.0 grains of H2O (5.96 ml) Winchester 93.8 grains of H2O (6.08 ml) Norma 95.5 grains of H2O (6.19 ml)
.300 Winchester Magnum SAAMI cartridge dimensions. All sizes in inches (in) and millimeters (mm). The projectile diameter should be 0.309 in (7.85mm)
SAAMI recommends a bore diameter of and a groove diameter of . SAAMI recommended a six-groove barrel with each groove being wide. Recommended twist ratio is 1:10 (254 mm). C.I.P. defines the common rifling twist rate for this cartridge as 254 mm (1 in 10 in), 6 grooves, Ø lands = , Ø grooves = , land width = , and the primer type is large rifle magnum.
The SAAMI Maximum Average Pressure (MAP) for this cartridge is piezo pressure (54,000 CUP). According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings, the .300 Winchester Magnum can handle up to Pmax piezo pressure. In C.I.P. regulated countries, every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. This means that .300 Winchester Magnum-chambered arms in C.I.P.-regulated countries are currently (2013) proof-tested at PE piezoelectric pressure.
Performance
The .300 Winchester Magnum can stabilize bullet weights ranging from 110 to 220 grains and is used for applications such as big-game hunting, benchrest shooting, and military purposes.
The most useful bullet weights for the .300 Winchester Magnum are those weighing between . However, bullets weighing between are available to the reloader for the .300 Winchester Magnum.
150-grain bullets Although the 150 grain bullet may have a lower ballistic coefficient than heavier alternatives, this is compensated by its high velocities, which extend its maximum point blank range, making it suitable for light-skinned big game such as deer and sheep, up to considerable distances. Winchester's factory ammunition for the .300 Winchester Magnum is capable of with the bullet and with the bullet, however old Western "Power Point" soft point can reach past with projectiles. The maximum point blank range for the bullet is yards when zeroed at . The maximum point blank range for the bullet is 300 yards when zeroed at . The ability to zero the .300 Winchester Magnum and shoot without holdover to makes the cartridge one of the flatter-shooting cartridges.
165-grain bullets The 165-grain bullet has a higher ballistic coefficient than a similarly shaped 150-grain bullet while maintaining very high velocity, resulting in a flatter trajectory. Usually, a 165-grain bullet shot from a .300 Win Mag has a muzzle velocity of approximately 3160 fps, which is 100 to 150 fps slower than the lighter 150-grain bullet. Similar 168-grain bullets are also popular among the .300 Win Mag and other .30-caliber magnum cartridges.
180-grain bullets Probably the most popular weight for the 300 Win Mag is the 180-grain bullet, with a high ballistic coefficient and capable of taking down light-skinned big game of any weight. The 180- and 185-grain bullets are also considered the most versatile, with a muzzle velocity of 2950 fps from average factory loads.
190 to 220-grain bullets Due to their high ballistic coefficients, heavier bullets are usually preferred by long-range shooters, as they are extremely efficient at bucking wind and carrying downrange energy capable of taking down game of any size in America and Europe. These bullets are generally loaded to reach muzzle velocities of 2700 to 2800 fps.
Comparison with other .30 caliber big game cartridges Cartridge Criteria Muzzle .308 Winchester (Winchester – SXP308) Velocity Energy .30-06 Springfield (Remington – PRA3006B) Velocity Energy .300 Winchester Magnum (Winchester – SXP300WM) Velocity Energy .300 Weatherby Magnum (Weatherby – N300180ACB) Velocity Energy Values courtesy of respective manufacturers Compared with the 30-06 Springfield the .300 Winchester Magnum provides a roughly increase in velocity. This translates to about 20% greater energy advantage over the 30-06 Springfield cartridge. Due to the short neck, heavier bullets, particularly those weighing greater than and mono-metal bullets such as the Barnes X bullets, will need to be seated more deeply into the cartridge. As the bullet takes up volume that the propellant could have occupied, the velocity advantage diminishes as the bullet's weight increases.
The .300 Winchester Magnum is known for its accuracy and has been used in - and -yard competitions. While in hunting situations, such accuracy is unnecessary, it does aid in extending the cartridge's range. Taken together with its performance, it remains one of the most useful and popular cartridges today.
Although cartridges such as the .30-378 Weatherby Magnum, .300 Remington Ultra Magnum, and the .300 Weatherby Magnum all exceed the performance of the .300 Winchester Magnum. None of these cartridges can be chambered in a standard-length action. Few .30-caliber (7.62 mm) standard-length cartridges match the performance and versatility of the .300 Winchester Magnum.