I'm a machinist and I send some of my projects to Casey at Tactical Ordnance. I have visited him, and believe me, he has a professionally equipped shop. Casey is capable and not just competant, he's talented. On top of it all, he's timely.
Gunsmiths who use cheap hobby-grade machines and discount tooling should be avoided for a manufacturing job like this, IMPO. Sometimes, you can go wrong...
From a 24" blank, you ought to be able to get a 14.5" barrel and a 10.3" barrel, if you are careful with sawing and facing/crowning.