7×64mm

7x64mm

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 weight/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" [1][2]

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.

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 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.

Beside the 7×64mm 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 7×65mmR variant of the cartridge was also immediately a commercial success.

In countries where military service cartridges are banned for civil ownership (like previously France), the 7×64 Brennecke is a successful cartridge for hunting and marksmanship.

Cartridge dimensions

The 7×64mm has 4.48 ml (69 grains H2O) cartridge case capacity. A sign of the era in which the 7×64mm 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 C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 7×64mm Mauser can handle up to 415.00 MPa (60,191 psi) Pmax 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. This means that 7×64mm Mauser chambered arms in C.I.P. regulated countries are currently (2014) proof tested at 519.00 MPa (75,275 psi) PE piezo pressure.[3]

The SAAMI Maximum Average Pressure (MAP) for this cartridge is 55,000 psi (379.21 MPa) piezo pressure.[4]

The American .280 Remington cartridge is probably the closest ballistic twin of the 7×64mm. When compared to the 7×64mm, the .280 Remington has a slightly lower maximum allowed chamber pressure and as an American 7 mm cartridge has a slightly smaller bore. European 7mm cartridges all have 7.24 mm (0.285 in) grooves Ø diameter. American 7mm cartridges have 7.21 mm (0.284 in) grooves Ø.

Contemporary use

As noted, the 7×64mm is one of the favorite rifle cartridges in Central Europe and is offered as a chambering option in every major European hunting rifle manufacturer's products palette. The versatility of the 7×64mm for hunting all kinds of European game and the availability of numerous factory loads all attribute to the 7×64mm chambering popularity.[5] 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 7×64mm 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 7×64mm rimmed sister cartridge, the 7×65mmR, is also very popular in Central Europe for the same reasons as the 7×64mm. The former legal banning of (ex) military service cartridges like the .308 Winchester, 7×57mm Mauser, 8×57mm I, 8×57mm IS and the .30-06 Springfield in countries like France and Belgium also promoted acceptance and use of the 7×64mm and the 7×65mmR.

See also

References

  1. ↑ Barnes, Frank C. (1997) [1965]. McPherson, M.L., ed. Cartridges of the World (8th Edition ed.). DBI Books. pp. 355, 374. ISBN 0-87349-178-5.
  2. ↑ RWS 11.2 g HMK datasheet
  3. ↑ C.I.P. TDCC sheet 7 x 64
  4. ↑ ANSI/SAAMI Velocity & Pressure Data: Centerfire Rifle
  5. ↑ The RWS Ammunition Ballistic Data & Application Consultant shows several 7x64mm factory loads

External links

Wikimedia Commons has media related to 7x64 Norma.