I'm lost here. You want .20 caliber but not .204? Not much out there really. You could look at something like 6br, or even 22br. There are lots of hot .22 caliber rounds. You can go from ultra fast to very high BC and anywhere in between. You can look for a wildcat all you want, but in the end, a lot of factory made chamberings are done so because they are a quality design. .22-250 is going to stick it to the .204 in a lot of ways. What the .204 does better, something like say a .22hornet necked down to .204 would do even better. I would personally probably go out, buy a 1:9" twist quality .223 rifle, load up some light bullets for exploding varmints, and load up some 69gr loads for longer shots and have fun. But that may be too plain for your taste. Rather have something that sounds cool than something practical.
