Abstract: A multiple barrel firearm having "over-and-under" barrels or "side-by-side" barrels is adapted to have individual ones of the barrels fired by successive pulls of a single trigger. Upon discharge of one of the barrels a recoil and counter-recoil responsive means, such as an inertia block pivotably mounted on the trigger is mechanically positioned to engage a hammer trip lever associated with the second barrel to assure that the second barrel is fired upon a successive pull of the trigger. This is accomplished by thrusting a cam lug into the path of movement of the recoil and counter-recoil responsive means during its counter-recoil movement so as to disengage it from means normally holding the recoil and counter-recoil responsive means out of engagement with the trip lever prior to firing of the first barrel.