yes, most are on the bottom but you see stock magazine on top from time to time

a common drilling have the rifle barrel on the bottom because the force working against the breech when fired is much greater

- when the the barrel is a rifle barrel
- when the rifle barrel is higher, that means further away from the locking mechanism

so they having the barrel firing first ( what means firing more often) on the bottom and the barrel fired the second time on top. its not that the action can not withstand it safely but any break action will come loose sooner or later and its only a question of how many rounds you fire with this gun. to make the action working as long as possible before you have to repair the locking mechanism you try to reduce the force against the breech as much as possible.