What velocity are you getting out of the 70 grain ballistic tip?
I've not worked with the .243 much. My experience with that bore diameter is 99.9% from a slow twist 6x.284. I shot mostly 70 grain ballistic tips, but at roughly 3850 fps at the muzzle. Until a couple years ago when I got into .204, that 6x.284 was the most destructive thing I've ever used on varmints including .22-250 and .220 Swift. The 65 grain VMAX was a little more explosive yet, but not quite as accurate.
If you're not happy with the 70 grain ballistic tip, you might want to try the 55 grain version. It's got a higher BC than the .22 cal 55 grain and in some rifles can be launched over 4000 fps, so you've got both higher BC, more velocity, and greater frontal area than the .22-250 or Swift with a 55 ... thus more splat downrange.
The 58 grain VMAX is more fragile yet but doesn't have quite the BC, nor in my gun, was not as accurate.
Tom
