I've never shot an elk with a 260, but have shot both Kudu and Eland with a 6.5x55. An Eland is bigger/tougher than most elk that I've seen, so if you are shooting a properly constructed bullet and can hit your POA, you should be OK. The smallest cartridge that I've used to shoot elk was a 7x57 and that elk died within a few steps.

Jeff