Welcome to the forum! :grin:
The 260 gr AB has a cannelure that will get you to the SAAMI spec.
I perfer to load about .015" off the lands or to the the magazine length,
depending on the caliber and rifle.
Try loading to just under your magazine length and see what kind of accuracy you are getting. You can always load shorter.
In my 375H&H which is a Win model 70 Stainless, my maximum cartridge O.A.L. is 3.910" !!! Since my magazine box is the limiting factor for me, being 3.6" long, I seated my 260 Accubonds to 3.590" If I may add, I'm using 73.0 grs of Reloader-15 for an average chronographed velocity 15' from the muzzle of 2750 FPS.