If you do go with a 22 based on the 243-sized case, you may wish to consider the 22 CHeetah MKII, with a few changes that I made to the design.
Basicly I went with a 1-in-9 twist and 0.100" longer throat to acomodate longer, heavier bullets. I'm shooting Sierra 103gn bullets at 3650 fps. This rig will slay prarie dogs at 800yds on a regular basis. It's on a Ruger action.
I start with 308 win. cases, not the BR cases because I like to use the large rifle primer. The original CHeetah and the MK2 are both based on the 308 win BR case, which has the small rifle primer pocket. This may work in Southern California, using the lighter bullets and faster powders, but for a long-range unit that may be used in cold weather, you need a large rifle primer at least. I'm shooting a hefty charge of WW WLR powder and lighting it with CCI BR4 primers.
I use 308 brass so that there is plenty of material in the neck for me to work with; I turn the outside of the necks for a .0015 thickness and fireform.
I call it the 22 CHeetah MK3.