The Izhevsk Mechanical Plant (Baikal) has developed an interesting shotgun designated as MR-133 that is fed from two magazines: a cylindrical underbarrel magazine that holds 6 cartridges and a box-type detachable one that accommodates 3 shells.
By changing position of the lever switch located on the detachable magazine, an operator can select feeding.
It is, no doubt, a handy feature, but it does not solve the problems of a manual slide action.