The cartridge owes its development to hunters requesting Holland & Holland to develop a cartridge that would have increased power over the .375 H&H Magnum. The project was undertaken by Russell Wilkin, the technical director for Holland & Holland. The result was two cartridges: the .400 H&H Magnum and the .465 H&H magnum. The cartridge was launched in 2003 to the public in 2003 in the UK and Europe and became available in North America in 2008. It follows in a long line of illustrious big bore cartridges introduced by Holland & Holland, the last of which was the
.700 Nitro Express. The .400 H&H Magnum is a modern rifle
cartridge designed for hunting large and dangerous game animals. The cartridge would be legal in countries which require a .400 minimum caliber for the hunting of dangerous game. ==Performance==