The German ammunition manufacturer Rheinisch-Westfälischen Sprengstofffabrik (RWS) [de] introduced both cartridges commercially in the spring of 1939.
In properly adapted standard military Gewehr 98 or Karabiner 98k service rifles the large 6.5×68mm cartridges are, however, praised for very smooth and reliable feeding.
The widespread availability of standard size Mauser 98 rifles and the fact that the .375 H&H Magnum cartridge and its necked down version the .300 H&H Magnum with approximately 72.4 mm case length were too long to fit in standard sized Mauser 98 bolt-action rifles makes the shorter 6.5×68mm, 8×68mm S and .375 Hölderlin interesting chambering options.
The cartridge became popular after World War II due to its high performance and flat trajectory, when German hunters were allowed again to own and hunt with full bore rifles.
A rare feature of this German rimless bottlenecked centerfire cartridge design is that it has a slightly rebated rim (P1-R1 = 0.3 mm).
(Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) guidelines the 6.5×68mm case can handle up to 440 MPa (63817 psi) piezo pressure.
This slow twist rate was chosen since the bullet jackets used in the 1930s were not strong enough to cope with the forces generated by the magnum muzzle velocities of the 6.5×68mm.
Due to the large case capacity in relation to the 6.5 mm (.264 inch) caliber bore size the 6.5×68mm is very harsh on barrels.
This makes this cartridge impractical for most competition shooters who tend to fire a lot of rounds in practice to acquire and maintain expert long-range marksmanship.
Practically there can be some muzzle velocity gained by this method, but the measured results between parent cartridges and their 'improved' wildcat offspring is often marginal.
Because the 6.5×68mm offers an exceptional sturdy, pressure resistant cartridge case that can relatively easily be reloaded with primers, powder and bullets and hence be reused several times it has become quite popular amongst wildcatters.