Having the muzzle turned for a guide bullet starter is not a regional thing. I just counted 28 rifles on my wall that are turned for a guide bullet starter, all of them by various Illinois makers. This count did not include percussion schuetzen rifles, which would add eight more. There is such a variation in diameter, length of turned section, decoration and more, that I question whether any of them came from a barrel blank supplier (Remington, Hitchcock & Muzzy, etc.) already turned. There would have been no need for it unless the rifle was intended to fire some type of bullet (usually a picket bullet) that requred it. These rifles usually have faster twist rifling, sometimes gain-twist, to stabilize a longer projectile. Likewise, I do not believe that many of these barrels were purchased from a supplier with rifling already in them. The rate of twist, number of grooves, style of lands and grooves, etc. is all over the map, as is bore diameter. Many of these local gunsmiths' claim to fame was that their rifling was superior to that of the gunsmith in the next town over, and more accurate.
