One of the guys I hunt ELK with almost every year hunts with a marlin 45/70. the load he uses,lately is the 405 remington bullets over 43 grains of imr 4198 (work up slowly its safe in his rifle it may be differant in yours)
he gets over 1750fps
he sights in 3.5" high at 100 yards and has a 170 yard zero, the rifle kills well out to just over 200 yards,if the single ELK he dropped at that range is proof, but only a single ELK has been shot at over 150 yards, most (hes killed 6 more that Im aware of)are shot at under 150 yards in the heavy timber where the ELK tend to stay holed up durring the day.
my late hunting partner used a 358 BLR, neither of these guys had trouble filling tags, some HUNTING SKILL, not long range snipeing is necessary but since even archery can kill elk when limited to less than about 1/5 that range I doubt youll have problems
I carry a 340weatherby most years but in over 33 years of ELK hunting I can only remember a few ELK shot by ANYONE in our ELK camp at over 250 yards simply because we hunt the timbered slopes as a 2 man team or two 2 man teams working togeather 90% of the time, with one to two guys blocking likely exit routes out of a canyon and one or two guys still hunting the ELK once the herd is located. this of course only works well if access to the canyons is limited, and your very familiar with the habits of the ELK in the area your hunting