The barrels are cut rifled with flat bottomed grooves in 4140 or 4150 material. I do know someone who can do cut rifled 8 grooves and lands. His barrels are of a radiused land type with wide grooves, and narrow lands. He made 2 baeels for me, one in his material, and one in mine. He uses 12L17 leaded steel, which is strong enough, and finishes like a mirror after rifling. My material was 4140 Resulpherized for a modern breechloader, and harder to rifle. Due to this additional hardness it does not have as smooth a finish. It needs to be lapped by hand. Either material will last a long time, it is up to you what you would want. I personally overuild my guns, but that is just me. The maker tells me that he has never see, one of the 12L17 barrels worn out with proper care in a Muzzleloader or shotgun. If you go with the 12L17 steel, and the 8 groove barrel, I probably could get it done for $175 or so. Let me know, and I will help get it done.
If you want rachet rifling or special profiles, it will cost alot. I asked several maker about it before, and was told that it would cost over $1000 just for the tooling. Then we would have to order 20 or more barrels. The deal I am working on know Hinges on getting a minimum of 6 barrels, preferaby 12 together for a run. He told he that his standard profile rifling would cost about $275-300 per blank.
I have to procure the blanks for him, or the cost would be even higher. There are very few people who can do this kind of work left. Some are not interested without signing a contract for a guaranteed number of barrels to offset the investment.
I can sent you a few slugs pushed through my barrels if you like, so you can see the profile of what is available. The only one I could not show you would be the run i am trying to set up with equal lands and groves from 8-16. Greg