I prefer 3FG over 2FG powder.

I would shoot 3FG 777. Try about 80-85 grains FFFG or95-100 grains FFGand the 250gr Shockwave from your Omega.

Reduce any FFG (2FG) max black powder/pyrodex loading data by 10% for the 3FG powder and then another 15% for the increased power of 777.

So reduce Max Black Powder/Pyrodex FFGloads by 25% when shooting 3FG 777.

Example:
Rifle's max load is 150 Grains loose Black Powder FFG. Your max 777 FFFG (3FG) load would be 112.5 grains loose. I would round down to 110 Max 3FG 777.

Good luck!

Tahquamenon