I went to the range today as I put a new scope on my Grendel... Again I am using an AR with a 16 inch barrel so keep that in mind. I am using BL-C2 powder and the 100 gr interlock (Discontinued)... I averaged 2428 FPS... I am using 30 grains of BL-c2 for the charge but could go higher... I just settled on this load and bullet because it shot very tiny groups...
All of that to say, with a 20 inch barrel and a bolt gun, I do not see you having any problems at all getting 2600... Alexander Arms has some load data but I understand that what they list is max loads (only one weight per powder listed). They have some powders and 100gr bullet combos over 2800 fps... I also understand they are using a 24 inch barrel bolt gun for their listed velocities...
Again, I am focused on group size and not velocities... this is the first load I shot through the chrono for the 6.5 Grendel and I had already settled on it due to the powder I had and the group size... (literally all touching making one hole at 100 yards - 3 shot groups)
hope that helps