Combination weapons are great when you have multiple seasons at the same time. Unfortunately, in the states, it's normally a one season deal. But, for a varmint hunter after fox or coyote, a shotgun barrel over a rifle barrel would make good sense. I have a couple of drillings, one is a normal 2x16 ga over an 8x57, and in the right barrel is a sleeve that shoots .22 magnum. They have two triggers, the front is a set trigger for the rifle barrel and with a selector also shoots the right shotgun or sleeved barrel. All are scoped, which are removable. My 'baby' is called a Bock (O/U) Drilling, 20ga mag over a 30-06 with a hornet barrel sandwiched on the right side. Scope is sighted in for the 30-06, the hornet barrel adjusts on the end to same POI, and the shotgun barrel is for shot which doesn't need to be sighted in. If you shoot slugs, you have to shoot a variety to find one that hits close.
A lot better than carrying two or three guns to the stand, I can be hunting deer, boar, rabbits, hare, fox, etc all with that one gun. And it comes in handy !!
But, like Billy said, they cost a bit more -- on the other hand, how much would you pay for 3 weapons? And you only need one scope!! Waidmannsheil, Dom.
Bockdrilling, Blaser BD880