The 7.5x55 Schmidt Rubin (7.5mm Swiss)
By Chuck Hawks
The 7.5x55 dates back to an 1883 black powder design by a Major Rubin, which he submitted to the Swiss military. The cartridge was adapted to smokeless powder and adopted by Switzerland in 1889 for use in a straight pull, rotating bolt action rifle designed in Switzerland at the Federal Armory, headed by Colonel Rudolph Schmidt. The Model 1889 Schmidt Rubin rifle had its locking lugs at the rear of the bolt, typical for bolt action designs of its time. The first version of the 7.5x55 was loaded with an odd 7.5mm (.3045") diameter bullet and operated at a maximum pressure of not more than 40,000 psi (as measured by the old crusher system).
The 7.5x55 cartridge has remained Swiss Army standard through a succession of four basic models of the Schmidt Rubin straight pull infantry rifle, and then was adapted to the Model 57 assault rifle, which went into widespread service sometime around 1980. The 7.5mm Swiss has got to be one of the oldest cartridges still in service with a modern army in the entire world.
The Schmidt Rubin Model 1889 rifle evolved into the Model 1896, which was stronger, and became the Model 1896/11 when it was converted to use the souped-up Mod. 11 (for 1911) cartridge. The Mod. 11 remains the current version of the 7.5mm Swiss cartridge.
Analogous to the "JS" version of the 8x57, the 1911 version of the 7.5x55 cartridge uses a .307" (7.62mm), 174 grain FMJ boat tail spitzer bullet at a muzzle velocity (MV) of 2640 fps. This higher velocity and higher pressure (46,000 psi) load with its larger diameter bullet cannot be used in the original Model 1889 rifle, but is safe in the Model 1896/11 and all subsequent versions of the Schmidt Rubin infantry rifle, which include the Model 1911 and Model 31. Unlike the Model 1889, these later versions of the straight pull, rotating bolt Schmidt Ruben rifle have their locking lugs at the front of the bolt. Note, however, that they leave a portion of the case head unsupported; if a case should rupture hot gasses can flow back through the action, destroying the rifle and injuring the shooter. Schmidt Rubin rifles are not suitable for "hot" reloads!
The 7.5mm Swiss cartridge itself is a modern looking creation that, like many European cartridges of the period, was clearly ahead of its time. It has a rimless (.495" rim diameter), bottle neck case with only moderate body taper and a sharp 30.5 degree shoulder angle. This case is 55mm (2.140") long and, despite retaining its "7.5mm" nomenclature, takes 7.62mm (.307-.308") bullets.
The performance of the 7.5x55 is comparable to that of the 7.62mm NATO (.308 Winchester) cartridge. Since the Swiss do not belong to NATO, they clearly saw no reason to change battle cartridges when they adopted a modern assault rifle. Commercial (hunting) ammunition for the 7.5x55 is loaded in Europe but not, as far as I know, in North America. Norma of Sweden offers 7.5x55 brass and loaded ammunition to shooters in the US.
Norma 7.5x55 factory loads give a 180 grain soft point bullet a MV of 2651 fps and muzzle energy of 2810 ft. lbs. The figures at 200 yards are 2223 fps and 1976 ft. lbs. The Norma trajectory figures for this load look like this: +2.2" at 100 yards, 0 at 200 yards, and -9.3" at 300 yards. So sighted, the 7.5x55 is a 250+ yard big game cartridge.
Since the 7.5x55 can be reloaded with standard .308" bullets, there is a vast selection of bullets available to the handloader, from 100 grains to 220 grains. The usual 150, 165 and 180 grain weights will do pretty much whatever can be done with the 7.5x55 as a big game hunting cartridge, so I will limit the discussion of handloads to those three bullet weights.
According to data published in the Hornady Handbook, Third Edition their 150 grain Spire Point bullet can be driven to a MV of 2400 fps by 38.4 grains of H4895 powder, and 2800 fps by 46.7 grains of H4895. The 200 yard figures for the latter are 2296 fps and 1757 ft. lbs. of energy. The trajectory of that load looks like this: +2" at 100 yards, 0 at 200 yards, -8.8" at 300 yards. Zero that load to hit 3" high at 100 yards and you should have about 275+ yard cartridge suitable for medium size big game, such as most species of deer and antelope.
Hornady's 165 grain Spire Point bullet can be driven to a MV of 2200 fps by 34.5 grains of H4895 powder, and a MV of 2700 fps by 45.5 grains of H4895. The 200 yard figures for the latter are 2257 fps and 1867 ft. lbs. The trajectory of that load looks like this: +2.1" at 100 yards, 0 at 200 yards, and -9.2" at 300 yards. This would be a good general purpose big game hunting load for a 7.5x55 rifle, particularly if it were zeroed to hit 3" high at 100 yards, which should extend the point blank range to about 275 yards.
The 180 grain Spire Point bullet can be driven to a MV of 2100 fps by 38.1 grains of IMR 4350 powder, and 2500 fps by 47.5 grains of IMR 4350. At 2500 fps the ME is 2499 ft. lbs. At 200 yards the bullet is still traveling at 2109 fps and carrying 1779 ft. lbs. of kinetic energy. The Hornady trajectory figures for this bullet look like this: +2.6" at 100 yards, 0 at 200 yards, and -10.5" at 300 yards. With this load the 7.5x55 is about a 250 yard hunting cartridge, adequate for game like North American elk and Swedish alg.
The 7.5x55 is a very old cartridge that looks and shoots modern. There is no reason it could not be used successfully for about 90% of all the world's big game hunting.
Copyright 2002, 2012 by Chuck Hawks. All rights reserved.