I'm also a new Omega owner, and it took me about 300 shots to find the right combo that gives me tight groups (I'm using 300 gr Shockwaves and 110 gr 777 powder).

I had the same problem you describe. I would get two dead on and third way off. I experimented with several different bullets, different sabots, and tried a couple propellents in various forms. I also learned to be very meticulous with cleaning between shots and making sure each shot left a barrel that was in the same condition as the previous shot.

My advice would be to try 777 and AP in various measures, to buy around 15 bullets from every manufacturer you can afford, use a couple different sabots, make sure your in-between shot routine is standardized, and above all, keep shooting. You will eventually find what works for you. Good luck