I finally picked up some IMR4166 to try out. When I try a new powder, you'll notice the velocities are always low. 
Thats so theres no surprises. 

IMR4166, 174gr Sierra Matchking
1. 47gr. 2628fps
2. 48gr. 2695
3. 49gr. 2752 (no over pressure signs)
More coming soon....

Vit N-540, 174gr Sierra Matchking
1. 53gr. 2950fps
2. 53.5gr 2964
3. 55.5gr 3073 (4shot avg)

23.7" barrel