I'm not sure any major benchrest .22 rf maker currently does ratchet rifling.  Shilen I think did, at one time.  But, since their ownership change a couple years ago, they have run into production problems and can't produce a barrel for delivery in the next 2 to 3 years.   

If I was trying to make an accurate rifle, I'd use Benchmark, Lilja, or Mark Chanlynn.  Benchmark would be the easiest to acquire and the most sure bet for accuracy, service and delivery.

That's not to say Lilja and Chanlynn aren't great.  I have barrels from both of them, and they're absolutely excellent.

Muller barrels are well regarded in benchrest, they have 13 twist in stock but only SS, and 27 inches.  (You need to Login or Register to view media files and links)

I wish I had some fast twist .22 rf barels to experiment with.  I may have to buy one, but it's a shame, as I have Flash Ebert/Turbo barrels, Pence Barrels, Benchmark Barrels, Hart, and maybe a couple others in my stock.  But, all 16 twist.

Northland Shooters Supply used to have Shilen blanks in stock but with the Shilen slow delivery issues this may not be the case now. You might give Northland a call to find out if he has anything on the shelf. Lilja's tight groove barrel is reportedly very good. I have one for a CPA that I have yet to fire.

I purchased a Brux a few weeks back from Bruno's Shooter Supply.