Your probably right but it is worth a look, maybe try some H-1000? If not no big deal my next one will get there.......Plan is to build a slow twist 6-284 and run 55 grain Noslers really fast. Man this crap is addicting
Your 22-243 AI is really close in capacity to the 22-6mm and the 223 WSSM. Look up pressure tested data for these cases, and you'll see where you need to be. 22-6 data is available in the new Hornady manual, 223 WSSM is even available online through Hodgdon.
The 6-284 should beat 55 grain 243 Win loads by 100-150 fps or so.
I say "should" because if you are using antiquated methods of estimating pressure, such as "reading primers", you will likely be running at higher pressure levels than comparable pressure tested rounds.