I recently acquired an Ultralight .257 Weatherby to be used for antelope at distances from 100 to approximately 500 yards. In the past I've used a 25-06 and 115 grain Combined Technology Ballistic Silvertip bullets, with good success and no complaints.
The most accurate load in my Weatherby, so far, is a load with 110 grain Nosler AccuBond bullets. I am getting 3/4 inch groups at 3450 ft/second. I have tried several loads with the 115 grain ballistic tip that shoot at around 1" at 100 yards, at around 3400 ft/second.
Would I be making a mistake to settle on the AccuBond load? The ballistic coefficient, according to Nosler, is .418 while the ballistic coefficient of the 115 grain ballistic tip is .453.
I personally feel you'll be as well suited as you were when using the 115 NBTCT. The true test will be at close range where any bullet will be tested to the extreme at that velocity. I'd rather have the 110AB on a close range shot than the 115 NBT, but both will work through the ribs.
If you need a better bullet that the 110NAB, I'd suggest you try Barnes TSX. My 7mm Wea copper fouled badly when pushing 140 TSXs at 3400, of course each rifle will be different and yours may not foul too much with the TSXs at those speeds.
You give up a bit in BC but you state your accuracy has improved with this bullet.
Terminally, the 110 gr Accubond will retain MUCH more weight after impact then the 115 gr CT. I would be amazed if the 110 gr did not out penetrate the 115 while still offering the quick expansion and bullet energy transfer that the Ballistic Tips are famous for.
In my opinion, the Accubond is about the best long range big game bullet from a commerical bullet maker. If they shoot in the rifle at hand, they are what I would recommend and use for a commerical bullet.
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
I have a 25 WSSM barrel for my Savage 16FCSS. In the 2006 hunting season I used to to take a deer and a 250+ lb hog using the 110 Accubonds. Deer was shot through the ribs/heart/lungs at around 120 yds and hog was shot at around 75 yards, both one shot kills.
With that 257 mag it will not matter which bullet you use out to 500 yards much. If you sight in 3 inches high at 100 yards you are only down about 7 inches at 400 thats only 7, 1/4 minute clicks and 21 inches at 500 is 15, 1/4 minute clicks. Those 257 Mags shoot pretty flat and they hit hard on antelope or deer. I have a 25-06 that I use for deer over bean fields in NC and I love the 117 Sierra bullets. BANG FLOP. With any bullet most any 25 caliber is a real killer.