After reading through this article at The Firearm Blog, I’d now like someone to do actual side by side ballistic testing of 5.7x28mm ammo vs .22 Magnum ammo. Both from pistol length barrels and carbine length barrels.
Off the top of my head, the best platform for this would be one of the T/C Encore or Contender guns. Because they’re modular, all you’d need to do would be to get a 16 inch .22 Magnum barrel, a 16 inch 5.7x28mm barrel for the rifle length test, and then get a set of 5 inch barrels in both calibers for the pistol test. This way you can eliminate barrel length as a variable in terminal performance.
As much as I love the .22 Magnum, it’s not (despite what the internet told you) the same ballistically as the 5.7 round. The round fired from the Five-seveN is a much more aerodynamic bullet, as well as using powder optimized for pistol use. Of course, this is probably one of those things that I’ll never actually get the chance to test, which is really too bad – I think I’d be an interesting side by side comparison.