Personally Id go for the 28 gauge frame size and the 6.5x57R, only if Chapuis would regulate for the 160gr round however. This would prove adequate for moose I think, given good bullet construction and placement as always. It would make for a slim and trim little rifle that would recoil less than the 8x57R. Im thinking about a 6.5x53R based on a 20 gauge shotgun action, hence my preference for the 6.5.