Will it harm a rifled barrel to fire buckshot through it?

I have no personal experience with this. What follows is information from a reputable local gun dealer. Rifled barrels are designed primarily for use with sabot slugs. Buckshot will not harm a rifled barrel because in the barrel, the plastic wadding holding the shot together will be the only portion of the projectile(s) in contact with the barrel. Firing rifled lead slugs will lead to difficult (nearly impossible) to clean out accumulations of lead in the barrel & negate the rifling because the rifling of the slug & the rifling of the barrel will not match up.