.375 Holland & Holland Magnum - Design & Specifications

Design & Specifications

The .375 H&H Magnum case design was conceived to use cordite; a stick type propellant used widely in the United Kingdom. The tapering cartridge body design and the small shallow shoulder are typical aspects of cartridges optimized for the use of this propellant. An advantage of such a case design is that it will feed and extract smoothly thus contributing to the cartridge's reliability in the field.

Unlike previous cartridges, the .375 H&H operates at relatively higher pressures and was designed from the outset for use with smokeless powders that can generate higher pressures and thus higher velocities. However, when the cartridge was designed pressure levels were held to 47,000 psi (3,200 bar) as cordite was sensitive to temperature and could cause dangerously high pressures in the hot tropical climates of Africa and India. However, modern smokeless powders are not as sensitive to ambient temperatures as cordite and therefore both the CIP and SAAMI provide far higher allowable pressures than the original loading of the cartridge allowed.

CIP recommends that commencement of rifling begin at 8.91 mm (0.351 in). Bore diameter is given as 9.30 mm (0.366 in) and groove diameter is 9.55 mm (0.376 in). CIP recommends a six grove barrel contour with each grove having an arc length of 2.92 mm (0.115 in) and a twist rate of one rotation in 305 mm (12.0 in). Maximum chamber pressure is given at 4,300 bar (62,000 psi). There are no discrepancies between SAAMI and CIP values. However, CIP measures angle α (shoulder angle) as 29°55'43". SAAMI measure the shoulder angle as α/2 which is given by SAAMI to be 15°.