The Nagant Revolver was designed and produced by Belgian industrialist Léon Nagant. Adopted by police and military services of Sweden (7.5 mm M1887), Norway (M1893), Poland, France (8 mm), and Greece (Peristrofon M1895), among others. Of these only the largest user, Russia, issued revolvers that had the gas seal system.
Léon Nagant and his brother Emile were well known in the Russian Tsar's court and military administration because of the important part they had played in the design of the Russian service rifle Mosin-Nagant Model 1891. The Nagant M1895 became the standard issue side arm for Russian army and police officers, later including their special services, the NKVD and the KGB.
Production began in Liège, Belgium, but was soon moved to Russia. The M1895 started to be replaced by the more modern Tokarev semi-automatic pistol in 1933 but was still produced and used in great numbers during the Great Patriotic War. The distinctive shape and name helped it achieve cult status in Russia, and in the early 1930s the presentation of a Nagant M1895 revolver with an embossed Red Star was one of the greatest honours that could be bestowed on a Party Member. Production and usage continued until 1950, making it one of the longest-serving side arms in modern military history, but not longer than the Webley Service Revolver (1887-1963) and the Colt M1911 (1911-1984). It remains in use with the Russian Railways and remote police forces.
 Technical Characteristics
Non-gas seal revolvers have a small gap between the cylinder and the barrel; the small gap between the cylinder and barrel is necessary to allow the revolver's cylinder to revolve, presenting a new, loaded chamber for firing. This necessitates that the bullet jump the gap when fired, which may have an adverse effect on accuracy, especially if the barrel and chamber are misaligned, and also presents a path for the escape of high-pressure and high-temperature gases from behind the bullet. The M1895 has a mechanism which, as the hammer is cocked, first turns the cylinder and then moves it forward, closing the gap between the cylinder and the barrel. The cartridge, also unique, plays an important part in sealing the gun to the escape of propellant gases. The bullet is deeply seated, entirely within the cartridge case, and the case is slightly reduced in diameter at its mouth. The barrel features a short conical section at its rear; this accepts the mouth of the cartridge, completing the gas seal. By sealing the gap, the velocity of the bullet is increased by 50 to 150 ft/s (15 to 45 m/s).
This closed firing system meant that the Nagant revolver, unlike most other revolvers, could be effectively fitted with a far more silent suppressor, as indeed it was . During World War II, a small number of Nagant revolvers used by Russian recon and scout troops were outfitted with a variety of sound suppressor known as the “Bramit device.” The Cheka/NKVD/KGB were known to use the silenced Nagant for assassinations. Silenced Nagant revolvers, modified in clandestine metal shops, also turned up in the hands of Viet Cong guerrillas during the Vietnam War as assassination weapons. There is an example of a silenced Nagant M1895 in the CIA Museum in Langley, Virginia.
However, success had its price. Nagant revolvers had to be reloaded one cartridge at a time through a loading gate with the need to manually eject each of the used cartridges making reloading laborious and time-consuming.
The Nagant M1895 was made in both single-action and double-action models before and during World War I; they are known colloquially as the “Private model” and the “Officer’s model”, respectively. Production of the single-action model seems to have stopped after 1918, with some exceptions, including examples made for target competition. Most single-action revolvers were later converted to double-action, making original single-action revolvers rather rare.
7.62 mm Nagant is also known as 7.62x38mmR (Rimmed) or "Cartridge, Type R." The projectile is seated below the mouth of the cartridge, with the cartridge crimp sitting just above the bullet. When fired the crimp expands into the forcing cone, completing the gas seal and ostensibly increasing muzzle velocity by approximately 75 ft/s.
The 7.62 mm calibre was chosen, in part, to simplify the tooling used in barrel-making and manufacture of projectiles—the Russian service rifle of the time—the Mosin Nagant M91 featured an identical bore diameter, being chambered for the 7.62x54R rifle cartridge.
Handloading supplies (particularly proper brass) which were once relatively difficult to obtain, are now readily available for the 7.62 Nagant cartridge. Newly produced 7.62 Nagant ammunition is now available from Hotshot and Fiochi, and used cases from either company can be reloaded. New empty brass cases are available from Bertram. 100 grain wadcutter bullets of .311 inch diameter are also readily available. Dies, trimmers, and shell holders are available from Lee and RCBS, once again making 7.62 Nagant ammunition affordable.
Other cartridges—.32 S&W, .32 S&W Long, .32 H&R Magnum, and custom handloads using .32-20 Winchester, .30 Carbine or .223 Remington cases—will also chamber and fire in the revolver but will not achieve the gas seal.
you can see a bullet comparasion in my pictures.