I am fairly new to the 260 cartridge too.The 129 grain Hornady bullet works well for me with 46.5 grains of reloader #19 powder in Rem cases with CCI large rifle primers.
The usual disclaimer. Now that the legalities are out of the way, my rifle prefers 43.0 grains of H-414 and the carbine likes 44.0 grains of H-380. They both love the 129 Hornady. I sure hope I got those loads right!
I haven't used the 129gr Hornady, however, my 1 in 8 twist 25inch 260 Rem likes the 120gr Nosler Ballistic Tips with 43gr H4350, ~2850fps. I get 0.6MOA at 100m and 0.3MOA at 200m! Aussie Hunter
With the hornady 129 Ive been getting 2850 fps with 48gr RL-22 or 46gr of IMR4831. Both are max loads in my rifle and the RL-22 load shoots slightly tighter groups than the 4831 loads.::MV
