The .416 Rigby is a large-caliber rifle cartridge developed in the United Kingdom by John Rigby & Company for hunting dangerous game animals.
Designed in 1911, the .416 Rigby has the distinction of being the first cartridge to have a bullet diameter of .416 inches (10.57mm).
Two major firearms developments at the turn of the 20th century contribute to its success as a hunting rifle cartridge; The first is the development of cordite smokeless propellant in 1889, with the second being the creation of the Gewehr 98 bolt-action rifle by Mauser.
The Gewehr 98's bolt action, refined by Paul Mauser, had provided to gunmakers an inexpensive alternative to the single-shot and double express rifles which had dominated the dangerous game hunting scene for years.
At the turn of the 20th century, three major British gunmakers, Jeffery, Rigby, and Westley Richards, each designed a cartridge that could operate in the Magnum Mauser action and could offer large bore Nitro Express-level performance and ballistics in a magazine rifle, which was what British referred to as their own bolt-action rifles. The result was the introduction of the .404 Jeffery, .416 Rigby, and .425 Westley Richards cartridges, respectively. Their performance on game animals matched that of the larger Nitro Express cartridges, due to the sectional density of the projectiles (greater than 7.6mm or 0.300") and higher muzzle velocities (~700 m/s or 2,300 ft/s).
The first rifles that were chambered in .416 Rigby used the Magnum Mauser Square Bridge No. 5 action, as its large bolt face was easily adopted for use with the cartridge. With the Magnum Mauser action becoming more scarce after the second World War, .416 Rigby-chambered rifles were being built on Enfield P-17 and BRNO actions instead, as both of these, in turn, were based on the Gewehr 98 rifle.
With areas of hunting dangerous game on the decline since the end of WWII, interest in the .416 Rigby and most big bore cartridges began to decrease. By the 1970s, with Kynoch's demise as an entity, the .416 Rigby cartridge was in short supply. Many hunters set aside their .416 Rigby rifles, taking up the more popular .375 H&H Magnum or the .458 Winchester Magnum calibers.
With a renewal in interest in African game hunting, the demand for .416 Rigby cartridges and similar calibers began to grow. Companies such as Norma, Federal, and Hornady began manufacturing ammunition to meet the demand. The Kynoch brand name was licensed by Eley to Suffolk-based Kynamco, which continues to manufacture the .416 Rigby cartridge under the Kynoch name.
The .416 Rigby is a rimless, bottlenecked centerfire cartridge with slightly tapering walls. Originally designed to use strands of cordite as a propellant, the case is one of the most voluminous, allowing it to operate at moderate pressures. This, in turn, leads to good performance in regards to velocity and energy. Intended for use in Africa and India for hunting dangerous game, the cartridge's moderate pressure loading provided a safety margin against dangerously high pressure levels when used in tropical regions.
Its physical measurements and specifications are governed by the C.I.P., which mandates a six-groove barrel with a bore diameter of 10.36mm (.408 in) and a 10.57mm (.416 in) groove diameter, with each groove measuring 3.6mm (.142 in) wide, along with a twist rate of 1 in 16.53 inches (420mm).
The original 410 grain (27 gram) bullet had a sectional density of .338 inches and fired at a velocity of 2,300 feet per second (700 meters per second) and generated a muzzle energy of 4,702 foot pounds of force (6,375 joules). This energy is comparable to the .450 Nitro Express, which, until the ban of .458 caliber (11.6mm) cartridges in India and the Sudan in the early 1900s, was the standard of measure for dangerous game rifles. The cartridge was later standardized with a 400 grain (25.91 gram) bullet fired at 2,400 ft/s (731.52 m/s).
The .416 Rigby case was of a bespoke design, as it was not based on any pre-existing parent cases during its development. It went on to become the parent of several other modern cartridges (i.e. .338 Lapua Magnum) and even inspiring the conception of new cartridge designs, such as the .378 Weatherby Magnum series.