I have a Caywood NW trade gun that has a 20g smooth barrel and a .54 rifle barrel. I dont figure on changing the barrel every day, but have done it 3 or 4 times at least. Just be careful with the pins. It's not hard at all. I use a finish nail to start them out, then use pliers to carefully pull them out. Pull the screw out of the tang and the screw for the front strap thingy also if you have one, cause it also goes thru a barrel lug. (cant think of the words for the front strap thingy, but its the thing the shoulder strap goes thru) I loosen the lock a bit too, and I think the Caywood site tells you to do that. My fear is losing the pins, make sure to keep good track of them.
I have been using the rifle barrel 99% of the time, at least until I get or borrow a mold for .60 balls. My rifle barrel shoots great from a bench, and if I dont flinch and actually aim, it shoots great offhand.
Short answer... it is easy if you are careful, and my rifle barrel shoots much better than I do. I recommend the second barrel.
Jeff