Just because a set snaps right on does not mean they fit properly. There are several things that need to be carefully checked to determine whether they will function, and stay on face for an extended period of time. Amount of contact between the barrels and the breech face, amount of space between the barrel flats and the action flat, top lever position after closing, etc.

Fitting barrels is an extremely tedious job, not for the occasional hobbyist. It can be learned, but you should expect to pay "dues" to learn the procedure. If, and I mean if, you can find a gunsmith that has this mastered, don't bother with trying to learn yourself. Pay a master to do it. You will be way ahead. JMO, YMMV.

SRH

May God bless America and those who defend her.