I suspect that Mr. Boon really doesn't understand what is involved. As Jim says, you can't ream smaller, but reaming a .308 barrel out to .35 caliber and rerifling it is an expensive proposition and it is pretty hard to find someone to do it. If the gun owner wants to go to another caliber, it would probably be more feasible to just rebarrel or trade the rifle in on one in the caliber wanted.
Harry and Mete,
Several people I know are toying with the idea of reaming and re-rifling a barrel (high power, not a liner). From your responses, it appears you do that work all the time. Can I get an idea of the cost involved and a ballpark turnaround time?
Jim