I'm not sure about this but it would seem that deer will need a tighter pattern than say a goose, probally really need more than one pellet in it. I would doubt that you'd want to shoot at a deer all that far with buckshot. I'd think a full choke. Probally a better idea is to go to slugs.I understand that they do well out to 100yds, give or take. Then it's simple, buy a slug gun!
The only experience I have had with buck shot would be using 2 3/4 9 pellet 00 buck shot while using my super full choke I use for turkey hunting. 50 yds was about the limit. My buddy was using same set up only using 000 buck shot and he got much better penetration at the same distance. Shoud be sufficient for your set up. Definitely get the tightest pattern you can.
Your going to have quite a spread at 50 yards with buckshot regardless of the barrel, but full choke will give you the tightest group. Burneke(if that's the proper spelling) rifled slugs would be my choice.
Moose calling can get confusing to some, but cow calling is your main tool when moose hunting. If you go out and buy moose calls I would say you're wasting your money unless it is the birch bark cone. I find most store bought moose calls sounding worse than puffing a grunt your hands to make the call. You can roll up a piece of birch bark in a cone shape to use as a call and spend your money on a video that teaches you the basics of a cow call. A milk jug or a coffee can with a hole and a rope...