I know what counterboring is and why it might be done, but is it just a last ditch effort to save a shot out barrel? In other words, is it something to avoid?
Darren007's reply is fundamentally correct, but some collectors avoid counterbored C&R rifles because a counterbore generally means the gun has seen heavy use and the rest of it is in less than pristine condition.
OTOH I've seen plenty of shot-out milsurps that weren't counterbored. Furthermore, many collectors- particularly those like myself who have caught Surplusitis- have an appreciation for ugly guns.