7.5×55mm Swiss

7.5×55mm GP 11
Two 7×57 cartridges (left) next to a 7.5×55mm / GP 11 (mid), .308 Win (right) and .223 Rem (far right)
Type	Rifle
Place of origin	Switzerland
Service history
In service	1889–present
Used by	Switzerland
Wars	World War II (Armed neutrality)
Production history
Designer	Eduard Rubin
Designed	1889
Produced	1889–present
Variants	GP90, GP90/03, GP90/23, GP 11
Specifications
Case type	Rimless, bottleneck
Bullet diameter	7.77 mm (0.306 in)
Neck diameter	8.50 mm (0.335 in)
Shoulder diameter	11.60 mm (0.457 in)
Base diameter	12.60 mm (0.496 in)
Rim diameter	12.65 mm (0.498 in)
Rim thickness	1.65 mm (0.065 in)
Case length	55.60 mm (2.189 in)
Overall length	77.70 mm (3.059 in)
Case capacity	4.22 cm3 (65.1 gr H2O)
Rifling twist	270 mm (1 in 10.63 in)
Primer type	Berdan or Boxer Large rifle
Maximum pressure	380 MPa (55,000 psi)
Ballistic performance
Bullet mass/type Velocity Energy 130 gr (8 g) SP 3,000 ft/s (910 m/s) 2,608 ft·lbf (3,536 J) 150 gr (10 g) SP 2,820 ft/s (860 m/s) 2,658 ft·lbf (3,604 J) 174 gr (11 g) GP 11 2,560 ft/s (780 m/s) 2,535 ft·lbf (3,437 J) 180 gr (12 g) SP 2,570 ft/s (780 m/s) 2,642 ft·lbf (3,582 J) 200 gr (13 g) SP 2,460 ft/s (750 m/s) 2,700 ft·lbf (3,700 J)
Source(s): Cartridges of the World

For the 7.5mm Swiss pistol round, see 7.5mm 1882 Ordnance

The 7.5×55mm Swiss or GP 11 (or unofficially 7.5×55mm Schmidt–Rubin) is a cartridge developed for the Swiss Army by 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 Colonel 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.

7.5 mm Swiss cartridges have been in Swiss Army service since 1889 in their Schmidt–Rubin Model 1889 rifles. Originally using PC 88 ("powder composition-88") rauchschwacher (literally "low smoke") cut tubular smokeless single-base powder relying on nitrocellulose as its propellant ingredient it was known as the Gewehrpatrone 1890 (GP90). The GP90 was loaded with a paper patched lead hollow based heeled steel capped round nose bullet. Starting from the rear of the nose section the bullets were wrapped around by 2 turns of paper, much like cotton patches were placed around the bullet of a musket. This paper patching was supposed to aid in the gas seal of the bullet and reduce metallic fouling of the barrel.

It was discovered that the primer of GP90 ammunition was far too corrosive so it was updated in 1903 to the GP90/03 cartridge.

Long after the discontinuation of the Schmidt–Rubin Model 1889 rifle in the Swiss Armed Forces the GP90/03 round was updated in 1923 and called the GP90/23, for use in shooting competitions. The GP90/23 discarded the paper patching around the bullet and was loaded with a full metal jacket non heeled round nose bullet. The PC 88 propellant shape was changed to square flakes.

GP90, GP90/03 and GP90/23 ammunition was available in 9 different variants, all models combined.

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 or the MOWAG Eagle Reconnaissance Vehicle. In this role, it is usually belt fed with GP 11 full metal jacket and GP 11 tracer rounds.