7×64mm

The 7x64mm (also unofficially known as the 7x64mm Brenneke, though its designers name officially never was added as a part of this cartridge name) is a rimless bottlenecked centerfire cartridge developed for hunting. As is customary in European cartridges the 7 denotes the 7 mm bullet caliber and the 64 denotes the 64 mm case length. The 7x64mm is a popular hunting cartridge in central Europe and can, due to its 11.95 mm case head diameter and 84 mm overall length, easily be chambered in standard sized Mauser 98 bolt action rifles.

History
At the start of the 20th century the famous German gun and ammunition designer Wilhelm Brenneke (1865–1951) was experimenting with the engineering concept of lengthening and other dimensional changes regarding standard cartridge cases like the M/88 cartridge case, then used by the German military in their Mauser Gewehr 98 rifles, to obtain extra muzzle velocity.

In 1912 Brenneke designed the commercially at the time rather unsuccessful 8x64mm S cartridge (again in production since 2001). It was intended as a ballistic upgrade option for the Mauser Gewehr 98 rifles that were then standard issue in the German military. The German military chose however to stick to their 8x57mm IS rifle cartridge avoiding rechambering their service rifles for a cartridge that due to its more favourable bore area to case volume ratio ballistically would outperform the .30-06 Springfield cartridge of the United States Army. Brenneke’s engineering concept to enlarge exterior cartridge case dimensions like overall length and slightly larger case head diameter compared to the German 8x57mm IS military cartridge case coupled to an increase in maximum pressure to create new for those days very powerful cartridges was essentially sound and he persisted in the development of new cartridges along this line.

In 1917 Brenneke necked down his 8x64mm S design of 1912 to 7 mm calibre and introduced it as 7x64mm and achieved a major commercial success. The 7x64mm offered compared to the 7x57mm about 10 to 12% extra muzzle velocity. This results in a flatter trajectory and better performance at longer range. In the years between World War I and World War II the 7x64mm was often regarded by German hunters as a “miracle cartridge” and dozens of different factory loads where available on the German market. It was that highly regarded the German Wehrmacht (Army) during the 1930s even considered replacing the 8x57mm IS in favour for the 7x64mm for their snipers. The Wehrmacht decided - just like the German army in 1912 - to stick to the 8x57mm IS cartridge for their Mauser Karabiner 98k to keep things as simple as possible in their logistical chain.

Beside the 7x64mm rifle cartridge Brenneke also designed a rimmed version for break action rifles such as double rifles and combination rifles as well as for single shot rifles such as the falling block action Ruger Nr 1. of the cartridge in 1917. The rimmed 7x65mm R variant of the cartridge was also immediately a commercial success.

In countries where military service cartridges are banned for civil ownership (like France), the 7x64 Brennecke is a successful cartridge for hunting and marksmanship.

Cartridge dimensions
The 7x64mm has 4.48 ml (69 grains H2O) cartridge case capacity. A sign of the era in which the 7x64mm was developed are the gently sloped shoulders. The exterior shape of the case was designed to promote reliable case feeding and extraction in bolt-action rifles, under extreme conditions.



7x64mm maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).

Americans would define the shoulder angle at alpha/2 ≈ 20.42 degrees. The common rifling twist rate for this cartridge is 220 mm (1 in 8.66 in), 4 grooves, Ø lands = 6.98 mm, Ø grooves = 7.24 mm, land width = 3.70 mm and the primer type is large rifle or large rifle magnum depending on the load.

According to the official with C.I.P. (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portative) guidelines the 7x64mm case can handle up to 415 MPa (60190 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.

The SAAMI Maximum Average Pressure (MAP) for this cartridge is 55000 psi piezo pressure.

The American .280 Remington cartridge is probably the closest ballistic twin of the 7x64mm. When compared to the 7x64mm the .280 Remington has a slightly lower maximum allowed chamber pressure and as an American 7 mm cartridge has a slightly smaller bore. European 7 mm cartridges all have 7.24 mm (0.285 in) grooves Ø diameter. American 7 mm cartridges have 7.21 mm (0.284 in) grooves Ø. 

Contemporary use
The 7x64mm is one of the favorite rifle cartridges in central Europe and is offered as a chambering option in every major European hunting rifle manufacturers products palette. The versatility of the 7x64mm for hunting all kinds of European game and the availability of numerous factory loads all attribute to the 7x64mm chambering popularity. Loaded with short light bullets it can be used on small European game like fox and geese or medium game such as roe deer and chamois. Loaded with long heavy bullets it can be used on big European game like boar, red deer, moose and brown bear. The 7x64mm offers very good penetrating ability due to a fast twist rate that enables it to fire long, heavy bullets with a high sectional density. The 7x64mm rimmed sister cartridge, the 7x65mm R, is also very popular in central Europe for the same reasons as the 7x64mm. The (former) legal banning of (ex) military service cartridges like the .308 Winchester, 7x57mm, 8x57mm I, 8x57mm IS and the .30-06 Springfield in countries like France and Belgium also promoted acceptance and use of the 7x64mm and the 7x65mm R.