Gentlemen I believe the concensus is correct, Rigby Flats are decorative. Such projections are not high enough to allow a tool to 'lock on' for barrel removal or replacement, also the steel of the period was usually soft and would show damage to its edges. Whatever the original intent was in making them is lost in time. They do look attractive but are somewhat labour intensive to make. It might be quicker to CNC mill them but you would have to make a lot of barrels to justify the time spent writing out the programming.
Harry
