7×64mm

7×64mm
From left to right 7×64mm, 7.92×57mm Mauser, .243 Winchester and .222 Remington
Type	Rifle
Place of origin	Germany
Service history
In service	Never issued
Production history
Designer	Wilhelm Brenneke
Designed	1917
Produced	1917 - present
Variants	7×65mmR (rimmed)
Specifications
Parent case	8×64mm S
Case type	Rimless, bottleneck
Bullet diameter	7.24 mm (0.285 in)
Neck diameter	7.95 mm (0.313 in)
Shoulder diameter	10.80 mm (0.425 in)
Base diameter	11.85 mm (0.467 in)
Rim diameter	11.95 mm (0.470 in)
Rim thickness	1.30 mm (0.051 in)
Case length	64.00 mm (2.520 in)
Overall length	84.00 mm (3.307 in)
Case capacity	4.48 cm3 (69.1 gr H2O)
Rifling twist	220 mm (1-8.66")
Primer type	Large rifle
Maximum pressure (C.I.P.)	415.00 MPa (60,191 psi)
Maximum pressure (SAAMI)	379.21 MPa (55,000 psi)
Ballistic performance
Bullet mass/type Velocity Energy 9.1 g (140 gr) SP 914 m/s (3,000 ft/s) 3,810 J (2,810 ft·lbf) 10.0 g (154 gr) SP 880 m/s (2,900 ft/s) 3,901 J (2,877 ft·lbf) 11.3 g (174 gr) SP 820 m/s (2,700 ft/s) 3,841 J (2,833 ft·lbf) 11.2 g (173 gr) RWS HMK 867 m/s (2,840 ft/s) 4,209 J (3,104 ft·lbf)
Source(s): "Cartridges of the World"

The 7×64mm (also unofficially known as the 7×64mm Brenneke, though its designer's 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 (2.5 in) case length. The 7×64mm is a popular hunting cartridge in Central Europe and can, due to its 11.95 mm (0.470 in) case head diameter and 84 mm (3.3 in) overall length, easily be chambered in Mauser 98 bolt action rifles that were then standard issue in the German military.

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 8×64mm 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 8×57mm 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 8×57mm 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 8×64mm S design of 1912 to 7mm calibre and introduced it as 7×64mm and achieved a major commercial success. The 7×64mm offered, compared to the 7×57mm Mauser, 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 7×64mm 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 Nazi German Wehrmacht (Army) during the 1930s even considered replacing the 8×57mm IS in favour for the 7×64mm for their snipers. The Wehrmacht decided — just like the German army in 1912 — to stick to the 8×57mm IS cartridge for their Mauser Karabiner 98k to keep things as simple as possible in their logistical chain.