I have a Marburg 590 shockwave which is a 12 gauge shoot gun. Would i be able to shoot this

You can also shoot at pistol range for closer targets.

I shot my mossburg 500 there so I see no reason why you can't

Only RIFLE slugs at range unless shooting trap or skeet, for trap or skeet, barrel length needs to be 26inches long. Gun range RIFLE barrel length can be any size, but RIFLE slugs only

Why not. I shoot my 12 gauge shotgun there. It's a great facility.

Yes