page_title: 7.5×55mm Swiss
section_title: GP 11 cartridge
hierarchical_section_title: 7.5×55mm Swiss / History of the cartridge variants / GP 11 cartridge
caption_attribution_description: Italiano: Munizione GP-11; esercito svizzero English: 7.5x55mm Swiss GP 11 (Gewehrpatrone 11) Swiss military issue rifle cartridges
context_page_description: The 7.5×55mm Swiss or GP 11 is a cartridge developed for the Swiss Army by mechanical engineer Lt. Col. Eduard Rubin for rifles based on Rudolf Schmidt's action design. The ammunition used by the Schmidt–Rubin Model 1889 rifle was one of the first to use 7.5 mm copper-jacketed rounds similar to those used today. The GP90 7.5×53.5mm round designed by Rubin was revolutionary in that the most popular military calibres used in Europe at the time were around 10 to 14 mm as opposed to 7.5 mm of the Schmidt–Rubin ammunition. The 7.5x55mm Swiss cartridge is similar in appearance to the slightly smaller 7.5x54mm French round though the two are not interchangeable.
context_section_description: In 1911 the metallurgy and bolt design in Swiss military rifles had advanced enough that a more powerful cartridge could be used in the Model 1911 rifles and Schmidt–Rubin 1896/11 rifles. The 7.5 mm Swiss round was updated to the completely non-corrosive Gewehrpatrone 1911 (GP 11). The bolt thrust of the GP 11 round is relatively high compared to many other service rounds used in the early 20th century. Besides being used in the Model 1911 rifles and Schmidt–Rubin 1896/11 rifles, GP 11 ammunition was also used in the MG 11 machine gun, K11 and K31 carbines as well as in the Stgw 57 battle rifle. The cartridge saw extensive service until the early 1990s with the standard rifles of Swiss servicemen, and still sees use by Swiss Army reservists and sport shooters, of which there are many. Furthermore, it is still the standard ammunition for the MG 51 general purpose machine gun used on many Swiss armored vehicles such as the Pz 87 "Leopard 2" tank and the MOWAG Eagle reconnaissance vehicle. In this role, it is usually belt fed with GP 11 full metal jacket and GP 11 tracer rounds.
  The GP 11 cartridge used double-base powder combining nitrocellulose (gun cotton) with about 30% nitroglycerin as propellants.
  The 11.3-gram (174.4 gr) full metal jacket GP 11 boat tail spitzer bullet was when adopted an innovative bullet design. The GP 11 bullet contained a lead-antimony core and its jacket was made of plated steel or tombac. Depending on the year of production the plating was made of copper, brass, nickel or copper-nickel. The GP 11 cartridge cases were made of brass (72% of copper and 28% zinc) or, from May 1943 to January 1947, due to supply shortages in Switzerland, of aluminum or steel. The GP 11 bullet offered good aerodynamic efficiency and ballistic performance with a ballistic coefficient (G1 BC) of 0.505 to 0.514. At 780 m/s (2,559 ft/s) muzzle velocity the standard GP 11 ball bullet retained supersonic velocity up to 800 m (874.9 yd) (V₈₀₀ ≈ Mach 1.1) under ICAO Standard Atmosphere conditions at sea level (air density ρ = 1.225 kg/m³). Even by 2011 standards, 800 m (875 yd) typical effective range is quite remarkable for a standard military rifle round that is more than a century old.
  Maximum range with the GP 11 under Swiss chosen atmospheric conditions (altitude = 800 m (2,625 ft), air pressure = 649 mm (25.55 in) Hg, temperature = 7 °C (45 °F)) equaling ICAO Standard Atmosphere conditions at 653.2 m (2,143 ft) (air density ρ = 1.150 kg/m³) is acquired when the barrel is elevated 37° and is muzzle velocity dependent.
  The GP 11 bullet set off the militaries of countries like Germany, the United States and the United Kingdom at the onset of and after World War I to develop and field similar full metal jacket boat tail spitzer bullets to improve the maximum range and long range performance of the full metal jacket flat based spitzer bullet designs they used.
  Since its introduction in 1911 the GP 11 cartridge featured some technical development. The projectile-seating in the cartridge case neck was improved by adding a cannelure on the bullet and crimping the case neck over time, resulting in 30 kgf (66 lbf) (1911), 50 kgf (110 lbf) (1929 modification), 100 kgf (220 lbf) (1942 modification) extraction force. In 1942 the square flake-shaped double-base propellant was replaced by tubular shaped double-base propellant. Further, there were minor developments regarding the projectiles, sealing and primers. GP 11 cartridges were mass-produced for the Swiss military in the ammunition factories in Altdorf and in Thun until 1994. The last 1994 produced ammunition had lot No. 349-94. Previously GP 11 was also produced in Rotenburg and Solothurn as other municipalities in Switzerland.
  GP 11 is regarded as highly accurate and well-manufactured service ammunition. For Swiss military service ammunition the primer-type is Berdan. Berdan-primed ammunition is not easy for reloading previously fired cartridges.
  In addition to the standard full metal jacket GP 11 rounds, specialty rounds were produced as well for the Swiss military. Armor-pi
caption: Swiss Army issue 10-round GP 11 pack
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