Since your going to be shooting an Omega, then you will have to adopt a good swabbing habit. For that reason TripleSe7en loose powder is where I would start. I would load 100 grains of it and a 250 grain Shockwave and have at her. Then swab the barrel good and do it all over again. I think you will be more then happy with the accuracy.

I personally shoot a lot of Goex. I shoot Goex because I shoot on average 5 times a week or more. Goex is cost effective. It is very dirty many people think but if you swab the barrel when needed I find it no more fowl then any of the other powders. For many years I shot Pyrodex and then Triple Se7en came out. I have a few rifles that really like Triple Se7en. I have other rifles that really like Pyrodex P. And still other rifles that think Goex is still the top powder there is. I guess what I am trying to say is you might have to experiment to see which powder your rifle likes and which powder your climate seems to agree with. But if I were starting out with that rifle it would be Triple Se7en. And I think you will see that the Shockwaves can be pushed pretty hard. I've pushed them in m Black Diamond XR all the way to 120 grain. I did not see any reason to shoo that much powder so I cut them back to 100 grains. The recoil was better, the accuracy was excellent, and the projectile had all the power I needed for my hunting situation...