RE: white mountain carbine
The White[/b] Mountain Carbine is one of those rifles that have gone through a series of changes. The early rifles had a very fast twist. I think it was 1-24 and then there were some that were 1-32 twist as I remember. Even some 1-48 twist rifles were there. You can also get a Green Mountain Drop in barrel in 21 inches for the rifle.
It probably has a 1-32 twist. They are great conical shooters. Most people shoot the maxiball and Great Plains Conicals out of them with excellent results. There is no reason why it will not shoot sabots also. I am sure you're going to like the rifle.