We had a muzzle loading hunter from Kansas (I think) he was. We (several of us) were gutting & cutting up a moose further up in the same logging block that had been shot by another hunter.
The fellow with the muzzleloader was using 100gr. 2F & .530" commercial ball in his .54 TC rifle. The shot was made at 170yards from the moose. The ball struck a rib going in, holed both lungs and
the heart and came to rest against the hide on the off side. The moose bolted for approx. 40yards & dropped dead mid stride.
He's the green hat'd guy kneeling, bottom right in the picture. I would suggest from this experience, that a .54 is a decent moose or elk calibre. I do personally prefer larger bores for moose, but
will admit they are not necessary. I like my .69 and my buddy really likes his .75 as they both tend to drop the moose in his tracks.