First, let me say I'm no expert, but I have grown up in Alaska and have harvested a number of moose.
I'm not sure what load bigbore used on his hunt, but since Ike mentioned the load he is using from his 15" brl. and said, "sound like moose medicine?" I would like to offer a couple suggestions:
1)I would not use a 300 grn JHP. I believe these would make great deer / black bear bullets, but I would want a bigger tougher bullet, for moose.
2)A good all-around bullet would be the Hornady 350 grn JRN.
3)If you like cast, a good 300 grn or bigger, Flat nosed bullet.
4)Want bigger & jacketed, a 400 grn + would be good, don't go to soft.
I've seen an average bull moose take a magnum JSP bullet at 75 yards through the on side shoulder and no part of that bullet made it to the off side rib cage - not even on the inside. It ran a ways and we finally found it, but I'm sure a better bullet w/ more penetration would have done a much better job!
Just want to be helpful to the fine people here that may get the chance to go moose hunting, especially a "once in a lifetime" tag like some states - I wouldn't want you to have bad memories from a bullet that wasn't up to the task for the shot presented!
Good luck & be safe!
Del