I was reading about the 120 grain Nosler E-Tip (BC .497 G-1) which is a solid projectile but supposed to expand down to 1800 FPS but still has a higher BC than some of the hundred grain bullets. This might add some range over the 100 grain TTSX with lower BC.
David Fortier posted these chronograph results for a 12.5" 6.5 Grendel and might help until you can chronograph your 12" 6.5 Grendel.
Alexander Arms 12.5 inch 6.5mm Grendel
Alexander Arms 100 grain Berger OTM 2470
Alexander Arms 123 grain Scenar OTM 2330
Velocity figures are 10 shot averages recorded on an Oehler 35P placed 12 feet from the muzzle 1,030 feet above Sea Level at an ambient temperature of 30 degrees F.
*Note the low temps with the 12.5 inch gun
David Fortier posted these chronograph results for a 12.5" 6.5 Grendel and might help until you can chronograph your 12" 6.5 Grendel.
Alexander Arms 12.5 inch 6.5mm Grendel
Alexander Arms 100 grain Berger OTM 2470
Alexander Arms 123 grain Scenar OTM 2330
Velocity figures are 10 shot averages recorded on an Oehler 35P placed 12 feet from the muzzle 1,030 feet above Sea Level at an ambient temperature of 30 degrees F.
*Note the low temps with the 12.5 inch gun