Myth Busting: .22 Magnum vs. 5.7x28mm

    Inevitably, Kel-Tec’s new .22 Magnum (WMR) chambered PMR-30 pistol will be compared to the FN Five-seveN pistol which fires the ballistically similar 5.7x28mm cartridge. If people are not saying it now, they will be soon saying that the .22 Magnum is the same as the 5.7x28mm. I used to say the same thing. It turns out that this is far from the truth.

    Kel-Tec PMR-30 pistol. Photo by Oleg Volk.
    FN Five-seveN USG

    Kel-Tec have stated [PDF Link] that a 40 grain .22 WMR round should reach a velocity of 1230 fps from the 4.3″ barrel of their PMR-30 pistol. This works out to 134.40 ft/lbs of energy.

    This is a significantly less than the FN Five-seveN USG (4.75″ barrel), which can push a 40 grain bullet at 2009 fps. This works out to 358.57 ft/lbs! Nearly three times as powerful as the .22 WMR! 1

    This does not mean that the .22 WMR is not a good cartridge. It simply means that the 5.7mm is optimized to be fired from a pistol, rather than the slower burning .22 WMR loads which are designed to be fired from a rifle.

    5.7x28mm. Image from Wikipedia.
    .22 Magnum / WMR. Image from Wikipedia.

    UPDATE: Added correct link to specs on Kel-Tec’s website : [PDF Link]

    1. I assume that the 5.8mm load mentioned above it a hot load. I also assume that Kel-Tec will be publishing the results of the best performing ammunition they could find 

    Steve Johnson

    I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!