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The .375 Holland & Holland Magnum, .375 H&H Magnum for short, is a medium-bore hunting rifle cartridge, designed by British based manufacturer Holland & Holland in 1912.[1] The .375 H&H was one of the earliest cartridges to feature a belt to maximise head space, and has formed the parent case for numerous other cartridges including the .375 Weatherby Magnum and .450 Marlin.[1]


With the increasing influence of German-made cartridges on hunting rifles, British manufacturers began to develop larger calibre cartridges to hunt big game.[1] Holland & Holland were among the first to release a competing cartridge to the Mauser developed 9.3×62mm that had become one of the most widespread and easy to obtain cartridges in the hunting world.[1] The .375 H&H Magnum was the result of their endeavours.

The .375 H&H was also novel in that it used cordite, and hence produced a relatively low (by modern standards) pressure of 47,000 PSI, which meant that the cartridge could be exctracted with relative ease (ie it would not deform as much as a higher pressure round).[1] Later developments of the cartridge replaced the cordite with more modern powder mixes, with the maximum pressure also increasing.[2]

The First World War and its aftermath prompted Holland & Holland to produce the .375 H&H on a more general basis for the first time, openly selling the cartridge to the general public in 1919.[1] The Second World War, however, was the key to the .375 H&H's continued success, as major manufacturers such as Winchester began focusing on the civilian market.[1] The cartridge of choice for the new wave of hunting rifles: The .375 H&H Magnum.

Design Details[]

The .375 H&H Magnum was designed from the ground up, with Holland & Holland designing a brand-new belted case for their new creation.[2] The overall design of the case was influenced by the choice of cordite as a propellent, which required a tapered casing with shallow shoulder for optimum performance.[1] This aided the extraction of the .375 H&H as it operated more smoothly with the mechanism of the rifle it was used in, a fact that helped to establish its reputation and popularity as a hunting cartridge.[1]


The figures below are based on the performance statistics of .375 H&H Magnum cartridges produced and sold by Hornady.

Name Muzzle Velocity (ft/s) Energy (ft-lbs)
250gr 375 GMX® Superformance 2,890 4,636
270gr Interlock® SP-RP 2,700 4,370
300gr DGX® 2,630 4,263
All figures from the Hornady website.[3]

These figures demonstrate that the .375 H&H Magnum is more powerful than its major rival, the 9.3×62mm Mauser, although the German cartridge is cheaper to obtain.[1] That said, popularity of the .375 H&H has been established by both its performance and reliability through use.[2]


The .375 H&H was produced with a couple of variations of its design, both of which had unique features to change the potential potentcy of the original design.

.375 "Flanged" Magnum[]

The competition version of the .375 H&H Magnum, and originally released alongside the original design.[1] Often used with a 300 grain bullet, the .375 Flanged fires at a lower pressure, but will also take down the largest of game animals as effectively as larger calibres.[2]

.375 H&H Ackley "Improved"[]

A version of the .375 H&H produced by P.O. Ackley, who hoped to improve the power of the standard cartridge.[1] Features a steeper, 40 degree shoulder slope, and is capable of firing a 270gr bullet at 2,830ft/s, a small improvement.[1] Although this cartridge may be used in chambers fitted for the standard round, there is a significant reduction in power as a result, meaning that an Ackley Improved chamber must be used for optimal performance.[1]

.375 Weatherby Magnum[]

Designed by Roy Weatherby in 1944, the .375 Weatherby Magnum essentially features minor modifications to the case design, and was the first cartridge to use the .375 H&H as a parent.[1] The Weatherby is capable of firing at higher pressures, and can achieve muzzle velocities of 2,800ft/s with a 300 gr bullet.[1]

As a parent cartridge[]

The .375 H&H Magnum was used as a basis for a number of other hunting cartridges, particularly the .470 Capstick, .458 Lott, .458 Winchester Magnum, .450 Ackley Magnum, .450 Barnes Supreme, .450 Mashburn Magnum, and the .450 Watts Magnum.