I am building a long range 250 Sav on Sav 12 action for hunting in October 2017.
I am using a Lilja 257-10" twist SS 3-groove barrel

In the past I have built
2000 VZ24 257 Roberts Ackley 10" twist Lothar Walther, shoots 117 gr Sierra 1.2" 5shots average 100 yards, 75 gr Vmax average 0.75" 5 shots 100 yards, 100 gr averages 1"
2012 Win1885 257 Roberts Ackley rimmed 9" twist Shilen stainless shoots 115 gr NBT just fine to 400 yards
2016 WinM70pre64 25-06 9" twist Shilen stainless, shoots 115 gr NBT just fine to 400 yards

In Quickload / Quicktarget and if I put in 250 sav 24" barrel, 105% powder fill ratio of IMR-4166 [Copper and temp coatings] for both 115 gr NBT moly and 100 gr NBT moly.
At muzzle the 100 gr is 59 kpsi 3000 fps
At muzzle the 115 gr is 63 kpsi 2850 fps

At 500 yards the 100 gr is 1964 fps down 8.19 moa from a 200 yard zero, and drifted 3.23 moa in a 10mph wind
At 500 yards the 115 gr is 1979 fps down 8.54 moa from a 200 yard zero, and drifted 2.84 moa in a 10mph wind

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. -Ernest Hemingway
The man who makes no mistakes does not usually make anything.-- Edward John Phelps