Converting .243 Win. brass to .22CHeetah has worked well for me, and others, using both Winchester and Lapua brass. I turn necks to .012" to make wall thickness uniform, which aids accuracy and is always good practice when reducing case necks, as it makes them thicker and tight necks can jump pressures dangerously. For fire forming I simply use what is about the equivalent of a hot .220 Swift load with IMR4064 and use it for prairie dogs, as there is no point in wasting bullets and barrels otherwise. The reformed cases then have shoulders blown out full and sharp and ready for full CHeetah loading. My most accurate .22 CHeetah ammo has been with Remington's small primer .308 B.R. brass and Remington 7-1/2 primer. But using this brass entails a good bit more work and case preparation and not worthwhile unless you have a rifle accurate enough to benefit from the accuracy edge. In recent times I've tended to use lighter bullets as lighter and better 40 and 45 grain bullets have come available and higher velocities obtainable. Though heavier bullets are more wind resistant when velocities are equal or nearly so, at CHeetah velocities the lighter bullets get where they're going so quick you don't need to do a lot of guessing and calculating for wind. Which, combined its fine accuracy, makes the .22 CHeetah an outstanding performer.
