While the 7x57mm made for a great military round, Paul Mauser’s 6.5mm version was intended for sporting use only. It has never seen service use. It is therefore legal even in countries that prohibit military cartridges for sporting use. Mauser doubled down on his concept in 1910 and released a rimmed version of his cartridge for break action guns, the 6.5x57mm R. Due to the popularity of break-action rifles and combination guns in Europe, the rimmed twin was a hit, too.
The case is too long at 2.232 inches to fit a short action. That is the only downside from a design standpoint when comparing it to some of its 6.5-competitors. And only if you’re convinced a standard length action is a true disadvantage. The case can hold up to 59 grains of water. That means it has space for enough power to drive even the heavier .264 bullets to respectable velocities. To appreciate this, consider the 6.5 Creedmoor holds just 52.5 grains of water.
Powder volume isn’t the only variable determining muzzle velocity, but 12% higher case capacity compensates for the more efficient burning inside a short fat case like the Creedmoor. The difference in maximum chamber pressure (56,000 psi vs. 62,000 psi) handicaps the 6×57 somewhat. The modern, higher pressure limit of the 6.5 Creedmoor is a big reason why it beats some of the old 6.5 classics in muzzle velocity. At least in most factory loads.
6.5x57mm Mauser Performance
Let’s compare performance between the 6.5x57mm Mauser and the 6.5 Creedmoor. We’ll ignore more powerful cartridges like the .26 Nosler and 6.5-300 Weatherby. They’re in a league of their own anyway.
For this comparison, I picked a 120-grain lead-free T.X.R.G. bullet from Sellier and Bellot since a factory load is available in both chamberings. The bullet has a G1 ballistic coefficient of 0.414. The data for Mauser’s 6.5mm was measured from a 23.6-inch barrel and the data for the Creedmoor from a 21.6-inch tube, so I added 50 fps to the advertised muzzle velocity of the latter to compensate for this difference.