I don't know about a moose, but a Elk antler is very porous & you just have a thin hard part around it til you get up to the ends of the tines.
That being said, you would have to find one Exactly the shape you want to keep out of the porous part. I think a large whitetail antler piece would be much better, more solid & easier to obtain than buying a elk antler & not finding what will work. It is even hard to get a pair of matching knife scales of any size out of a elk antler because the solid part is so thin, let alone a buttplate..