Gunsmithing Dialing In The Throat & Muzzle

For the Gunsmiths that dial in the throat and muzzle when chambering a barrel, are any of you able to use that method on an 18" and 20" barrel?
I never use that method, but on my PM 12x36 the spindle is short enough you could do a 20" barrel but that would be about the shortest. There are some newer Precision Matthews lathes with spindles shorter by a couple inches where you could do that with an 18" I believe.