can anyone tell me the maximum range of these two bullets, 260 with a bc of .473 @ 3400 fps and the 300 with a bc of .485 @ 3200 fps with a terminal velocity of 1800 fps ?

It depends a little on your elevation but around 900 yards with the 260s and with the 300g around 800 yards

And you can get 3400 fps with 260 and 3200 with a 300 that is amazing. How fast can you push the 350smk,also how many more grains of powder do you get with this Improved version?

The 300 load is 111 grains of IMR 7828 ssc at a velocity of 3200 fps. the sierra 350 load is 108 grains of reloader 25 at a velocity of 3005 fps. The rifle is a remington 700 sendaro rebarreled with a Brux .375 1-10" twist 31 inch barrel. Im still searching for the perfect load as the reloader 25 has a little too slow of a burn rate . I cant get enough rl 25 in the case .

Here's my suggestion. Go here and play with the numbers comparing the 260/300/350 SMK and see what you come up with. I bet the messing with numbers will be quite revealing! JBM - Calculations - Trajectory