Since you're shooting an Omega you might want to try the 460 grain No Excuse Conical. Load about 80 grains of Triple Se7en under them Whether a wad will help you would have to experiment with. They have a lot of weight and a lot of down range energy. I have never shot an elk with a muzzleloader so all I can do is guess how effective they would be. They would be my choice for a hunting projectile in your circumstances.

Another choice is the good old Thompson Center Maxi Ball (Not the Maxi Hunter). You can push these pretty hard and remember, they are 370 grains is weight. They should get good penetration and do a number on anything you want to poke a 1/2 inch hole through. I read on another forum where a person with an Omega was going to use them out west because they shot excellent out of his rifle with 100 grains of Pyrodex. (I think it was.. I'd better go back and check his post before I swear to it).

Then there are the Great Plains Conicals. They should shoot well out of the Omega... all you can do is put in the range time and try.