The double rifle, also known as a double-barreled rifle, is a rifle with two barrels mounted parallel to each other that can be fired simultaneously or sequentially in quick succession. Synonymous with big game hunting found primarily in Africa and Asia, the double rifle is a sporting weapon with very little military heritage.
Design
The double rifle is usually handcrafted and is considered by many to be the pinnacle of sporting rifle design. It is not designed for long-range accuracy but instead for the security of an immediate second shot. Double rifles are similar to Double barrel shotguns.
Action
As with double-barrelled shotguns, modern double rifles are all made with either sidelock or boxlock actions, although occasionally old hammer rifles can be found. The majority of double rifles have been built on the boxlock actions as it is a simpler design with fewer moving parts that can fail and consequently, it has an outstanding reputation for reliability. The sidelock action, with its lockwork operating behind the main action body, has exceptional inherent strength and as a result could be built on slimmer action sizes in proportion to the calibre, although it is far more labour-intensive to manufacture and so more expensive.
Most double rifles manufactured today, especially those designed for dangerous game, are manufactured with selective ejectors which greatly speeds reloading. However many old hunters preferred non-ejector rifles, feeling that with practice they could reload just as quickly, these rifles can still be found and usually attract a slightly lower price.
Barrels
Double rifles can come in two barrel configurations, over-and-under designs (usually abbreviated as O/U) where the two barrels are mounted vertically one on top of the other, or side-by-side (usually abbreviated as SxS) where the two barrels are mounted horizontally next to each other.
For dangerous game hunting, side-by-side rifles are usually preferred. This is for a number of reasons but predominantly because the barrels of an over-and-under gun must be pivoted much farther down to clear the lower barrel for reloading.
During manufacture the barrels of double rifles require "regulation" to ensure the bullet paths from both barrels are aimed at a common point of aim. This can be done to ensure either the bullets 1) parallel each other closely at all practical ranges, or 2) converge at a given range, beyond which they begin to diverge. Because of the need to regulate a rifle to a specific loading of its chambered cartridge, once regulated a double rifle cannot satisfactorily shoot bullets of different weights or velocities, as it usually affects the accuracy. The process of regulating a double rifle’s barrels is complex and can be time-consuming, significantly adding to the cost of the rifle.
Sights
Whilst many modern double rifles are fitted with telescopic sights, the need for fast target acquisition in the face of dangerous game led to the development of the "Express" iron sights. Express sights feature a very wide and shallow rear V, usually with a white line marking the bottom of the V. The purpose of express sights is to allow for well-aimed shots over moderate ranges when there is time for careful sighting and to allow the rifle to be pointed like a shotgun to stop the charge of a dangerous animal at very short range when there is little time for aiming.
Calibres
Double rifles have been produced in all calibres from to . Traditional British double rifle calibres include the Rook rifle, Black Powder Express and rimmed Nitro Express families of cartridges and many of these can still be obtained today. European makers tend to chamber their double rifles in metric rimmed calibres developed by European firms, although British and American cartridges are offered.
Variants known as Cape guns are similar designs, but one of the barrells on a Cape gun is a smoothbore for firing shotgun shells, while the other is a rifled barrell. This allows for hunting a wider variety of game with the same weapon. A long gun combining at least one rifled barrell and (usually) one smoothbore barrell is a Combination gun, and some rare examples have up to five different calibres in one firearm.