In the case size, AR comp should be about the perfect powder. H4895 also.
There's load data for H4895, and it's not great re: velocity. RL-15 is a little faster. Both are down > 150 fps in a 18" barrel to keep the pressure at 52kpsi vs. LeverEvolution. That's why I'm curious about AR-Comp, since I happen to have a good bit sitting around.
It's somewhere between Varget and RL-15 in burn-rate, but I don't know what the pressure curves look like in this case. I'm not trying to utmost velocity, I definitely am aiming for accuracy. This is why I don't like the temperature sensitive powders, I've been having a rough time with them with a > 30F temperature swing during the day. At the same time, I'd like to stay out of the transsonic zone from an 18" barrel at 1000yds, and prefer to avoid going over 52kpsi in doing so.