Re: .223 and IMR 4064
I use 25.5 with the 55's. It's about all you can get in the case. I worked well in both my 1:9 and 1:8 twist sticks. As I have a pound and want to try some 75's I'm trying 21 to 21.5 with some Hornadys.
My local shop was out of RL-15, Varget, BLC-2 and anything else I'd have preferred. 4064 happened to be $8 bucks a pound cheaper than the rest too.