barrel twist

I purchased the firearm from the OP of another thread on this forum. Here is the store listing for the custom smokeless build, with specs: In addition to the content from the store listing, I have learned that Ken Thiessen built this smokeless muzzleloader while he was working for Bullseye...

I know. Another dumb question. Despite having shot my inlines for years I've often wondered just how the .45 slug inside the .50 caliber sabot is given its twist. The sabot makes it bore tight, right? But most of the bullet is inside the sabot. How does the rifling "grip" the bullet itself...