John
Im sure a moose could be killed with a .243 Winchester using the right bullet put in exactly the right place. But THAT doesnt make the .243 a moose rifle.
Your 6.5X55 is a fine, long range deer cartridge
and it will kill a moose just as will the .243, but THAT does NOT make it a moose cartridge either!
When I stood by my downed 1400+ lb. moose with a 5-foot antler spread that stood OVER 6-feet at the shoulder with a liver the size of a wash tub
I felt that my .338 Winchester magnum using my handloaded 210 grain Nosler Partition bullet wasnt too-much-rifle to use.
But had I hit that moose with my .300 Savage using a 180 grain Nosler Partition, it would have killed that moose just as dead just as fast if I had the same bullet placement as I had with the .338 magnum.
I believe any reasonable .30 caliber (.300 Savage, .308 Winchester, .30-06 Springfield) firing a relatively heavy (180 grain minimum), high-quality bullet at with the reputation of giving good expansion and excellent penetration (like the Nosler Partition bullet) would be adequate for a large moose. You dont really need a .300 Whiz-Banger Super Magnum. Moose havent suddenly grown armor plate, but they are big, tough animals that cling HARD to life.
Therefore, a larger diameter, deep penetrating bullet is the key to making a good kill on such large, tough game. Something of a larger caliber would, I believe, be better
something like a .35 Whelen or a .358 Winchester using a 225 grain or a 250 grain Nosler Partition would do the trick as well.
Of course, I know from first-hand experience that a .338 Winchester Magnum shooting a .210 grain Nosler Partition bullet @ 3,020 fps works. Those large moose antlers decorating my big fireplace prove that.
Strength & Honor
Ron T.