Lilja, Douglas, Krieger, Pacnor, Shilen, Bartlein, Broughton, Lawton, . . .ok, my mouth is watering. These are all top quality barrel makers. Most supply blanks or turned blanks. A gunsmith will need to chamber, crrown and final finish the outside.

I mentioned the Shilen and Savage thing because that is the only bolt together custom method I have heard of.

One note. . .Savage has an inherent advantage over all other actions. Both lugs bear on the receiver because it isn't overconstrained. Without the pivoting bolthead, a bolt action design is over constrained. Worse yet, the trigger is pushing up on the bolt shaft.

Remington's advantage is almost every riflesmith has made a Remington which shoots well. The recipe is a known entity. It takes a machinist.