I've never heard that. In fact, over the years I've talked to 'smiths and barrel makers about switching out the barrel on my B-78 and no one has ever raised that issue. What DOES seem to be true, though, is that Browning doesn't sell only the barrel (or only an action) ... only full barreled actions, as a unit. But a gunsmith should be able to do a barrel switch with a barrel from somewhere else. Maybe it also depends on the model of the particular gun. Try asking under the "Gunsmithing" forum and see what those folks say.
