Generally the idea I find is that you use one grade weight higher outdoors. So for instance, if you use .20's for CQB, you'd use .23's for outdoors. That's the pattern I'm noticing.
Alas, my gun has a garbage fps and only fires @ 310 fps, so I'm stuck with .20's and .23's. :/
Also, a little off-topic, but cav, I noticed you're in Sheridan's animation program. Just a friendly hello from a Durham College Game Dev student!