I have two 1:8 260 Tikkas. The one closest to your application gets fed 100gr TTSX with IMR4350 and gets 2980 FPS. Yes I can get more out of it, but I don't need to for the hunting it gets used for. The four deer it disposed of this year didn't seem to complain. I also have some 4064 laying around I might experiment with, but if you work with it, post what you get and hopefully same me some time and ammo.
I was able to get great accuracy from IMR 4064 and 100 gr TTSX with Rem 9.5's at 43 grains. I started at 41 which was not impressive at all worked up in .5 grain increments and groups tightened right up. Been running the 120 for a long time and going to try the 100TTSX as my primary deer hunting round this season. I have read about IMR 4064 and 100's either NBT or TTSX being an accurate combination in a wide range of firearms. I believe MD had great accuracy with the 100 NBT IMR 4064 in a Tikka as well.
Good luck and shoot straight y'all
