I shot the 123 Scenar at 3k easily out if a 23" 1-8" .260 using Lapua brass and three or four different powders. You're WAY overthinking this thing....
Rick and I talked about your issue, as I have dope on the exact bullet/cartridge/twist combo.... and it's good dope. I had to adjust the BC and velocity slightly to make the program match actual drops.... but I've never seen a program that reflected perfectly straight out of the gate.
PS....
Bullet : .264, 123, Lapua Scenar GB489 6032
Useable Case Capaci: 46.678 grain H2O = 3.031 cm�
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length : 24.0 inch = 609.6 mm
Hodgdon H4831 SC 110.0 47.8 3.10 2981 95.0 62207 10088 1.111 ! Near Maximum !
