I would gladly use a .260 Rem on moose using a 160 gr. RN bullet, but I would
do it at 100 yds. or under.
Bingo!!!!! Give this man a cigar.
The exact same criteria that makes the 6.5X55 a proven slayer of Moose.
Shell Shucker, you probaly remember the old Dominion 160grKKSP's for it too I bet.
I remember my grand dad tooting the 6.5 caliber against his No4 Lee Enfiled, but seeing the dismal velocity offered in the old .303 Dominion ammo and that "foot long" 160gr KKSP's 6.5mm bullet for very reliable penetration, and the rather short ranges 100yds or less, I now see the comparison.

Maybe the modern monolithic wonders that are much lighter and fired at a higher MV, will do the same,...... maybe, ......but I doubt if they will add another 200yds plus over what Shell Shucker has stated, if reliability is to be guarenteed. Over 300yds? Use your money wisely, and bring lots of trail marking tape if you can find a blood trail.
Bravo Shell Shucker, a man who knows the 6.5X55 as a MooseSlayer well.
There are those who state, and I believe have already posted in this thread, that if you make a light hole in the vitals it will surely die. If the animal has to run a mile in any direction to make cover, this will suffice, I guess.
This is not the case,..... considering the thicker terrain here in the east, and the distance a wounded animal can travel, so I'm not sure it's an ethical statement, in woodland hunting of Moose.
The 260 should be legal anywhere, so the critter is your baby, once the shot is fired.