A typical 5.6x57mm factory load, therefore, is slower than most.220 Swift loads. Would one load both cartridges with the same weight bullets? The bigger case of the German design (49.1 grains of water compared to 47 grains) allows for higher speed. Of course, actual capacity depends on the brass, but in general, the 5.6mm has a slight advantage here. Combined with a slightly higher maximum chamber pressure (63,818 psi for the RWS cartridge vs. 62,000 psi for the .220 Swift), the 5.6×57 has what it takes to surpass the .220 Swift.
The preferred bullet weights go hand in hand with fitting twist rates: the 5.6mm is usually launched from barrels boasting a 1 in 9.84-inch twist while a 1 in 14 or 1 in 16-inch rifling is common for .220 Swift rifles. Different purpose, different design, I guess. The lighter, faster bullets that work well on small critters perform better in the Swift, and heavier bullets are better stabilized in a 5.6x57mm. This should translate into a small advantage when extending the range of .224 bullets in shooting competitions (less drift, more retained energy, and more drop). But 22-calibers are rarely used for extreme-range work, so this is insignificant. With custom barrels and adjusted twist rates, the difference between both cartridges starts to blur.
As mentioned, the intended use of the 5.6mm from R.W.S. was roe deer and chamois hunting. The cartridge shined in this role, but today chamois can not be legally hunted with bullets smaller than 6.5mm in Germany and smaller than 6mm in Slovenia. In Austria, the cartridge is still legal for shots on chamois, as far as I know. But fewer places to use a gun usually mean a drop in sales figures, both for rifles and ammunition. And that, for sure, leads to fewer and fewer factory ammo options in the long run.
Unknown 22 Cartridge Shoots Faster than 220 Swift — Ron Spomer Outdoors is written by Lukas Schulte for www.ronspomeroutdoors.com