The .700 Nitro Express is a big game rifle cartridge made by Holland & Holland, London, England. It was developed in the 1988 by Jim Bell and William Feldstein and built by H&H. Feldstein had tried unsuccessfully to get H&H to build a .600 Nitro Express for him, but they had already ceased production. However, when Bell and Feldstein produced the entirely new .700 Nitro Express cartridge, they were able to attract the interest of H&H, who was looking for a new big-bore cartridge. After production began, the backlog of orders was so great that it continues to this time (2007) and H&H has even restarted the production of .600 Nitro Express guns. 
In many respects this cartridge parallels the .600 Nitro Express, in that it is essentially a scaled-up version of that cartridge. but is somewhat more powerful, and fires a heavier 1000-grain (64.8 g) bullet. The case itself is a completely new case, not simply another case resized. Double rifles are extremely expensive (many will sell for US $60,000 or much more in 2005 American currency) and have generally been replaced by magazine-rifle rounds like the .458 Winchester. Single factory loaded .700 Nitro cartridges are available, typically at $100 each, although they have been sold on the internet for as little as $50. This round, like many other big bore cartridges, can be hand reloaded, drastically reducing the cost - although few users are likely to expend much of this massively-recoiling ammunition.
While the .700 Nitro Express is sometimes touted as the "most powerful commercial round in the world", by the manufacturer, this is not exactly true. The .700 Nitro Express double rifle is only available on a custom order basis, and has never seen regular production, while the .585 Nyati which is built under similar circumstances is significantly more powerful. Currently the most powerful rifle cartridge available on a commercial basis is the .50 BMG. Still, the .700 Nitro Express is a very powerful round, and is known worldwide by its reputation among serious big-game hunters. It's also referred to as the most powerful sporting cartridge in the world, and this may be accurate.
. However, doing so makes the action of the rifle used nearly inoperable (especially in the case of a boxlock or sidelock rifle), while at the same time rupturing the cartridge casing and the primer cap.
The typical average muzzle velocity of a factory-loaded cartridge is 2,000 ft/s (610