Firearm comprising: i) a firing mechanism comprising a trigger, a firing pin, a locking element suitable for being moved to lock or release the firing pin; ii) an arming device of the firearm comprising: - transmission means connected to the trigger and moveable by it; - an arming member comprising a plurality of engagement elements (151, 156, 157) suitable for engaging the transmission means and/or the firing pin and/or the locking element, in such a way that a pressure of the trigger corresponds to a movement of the transmission means, which, by rotating, engage the arming member which in turn moves the locking element to lock or release the firing pin and engages or disengages said firing pin; wherein the arming member comprises: a) a firing pin operating body comprising the firing pin engagement element for engagement with the firing pin; b) a lock operating body comprising the transmission engagement element for engagement with the transmission means and the lock engagement element for engagement with the locking element of the firing pin, wherein the firing pin operating body is engageable in rotation by the lock operating body to in turn be moved in rotation; c) a support pin for the rotatable support the firing pin operating body and of the lock operating body to permit the mutual engagement of the components. i) a firing mechanism comprising a trigger, a firing pin, a locking element suitable for being moved to lock or release the firing pin; ii) an arming device of the firearm comprising: - transmission means connected to the trigger and moveable by it; - an arming member comprising a plurality of engagement elements (151, 156, 157) suitable for engaging the transmission means and/or the firing pin and/or the locking element, in such a way that a pressure of the trigger corresponds to a movement of the transmission means, which, by rotating, engage the arming member which in turn moves the locking element to lock or release the firing pin and engages or disengages said firing pin; wherein the arming member comprises: a) a firing pin operating body comprising the firing pin engagement element for engagement with the firing pin; b) a lock operating body comprising the transmission engagement element for engagement with the transmission means and the lock engagement element for engagement with the locking element of the firing pin, wherein the firing pin operating body is engageable in rotation by the lock operating body to in turn be moved in rotation; c) a support pin for the rotatable support the firing pin operating body and of the lock operating body to permit the mutual engagement of the components. - transmission means connected to the trigger and moveable by it; - an arming member comprising a plurality of engagement elements (151, 156, 157) suitable for engaging the transmission means and/or the firing pin and/or the locking element, in such a way that a pressure of the trigger corresponds to a movement of the transmission means, which, by rotating, engage the arming member which in turn moves the locking element to lock or release the firing pin and engages or disengages said firing pin; wherein the arming member comprises: a) a firing pin operating body comprising the firing pin engagement element for engagement with the firing pin; b) a lock operating body comprising the transmission engagement element for engagement with the transmission means and the lock engagement element for engagement with the locking element of the firing pin, wherein the firing pin operating body is engageable in rotation by the lock operating body to in turn be moved in rotation; c) a support pin for the rotatable support the firing pin operating body and of the lock operating body to permit the mutual engagement of the components. a) a firing pin operating body comprising the firing pin engagement element for engagement with the firing pin; b) a lock operating body comprising the transmission engagement element for engagement with the transmission means and the lock engagement element for engagement with the locking element of the firing pin, wherein the firing pin operating body is engageable in rotation by the lock operating body to in turn be moved in rotation; c) a support pin for the rotatable support the firing pin operating body and of the lock operating body to permit the mutual engagement of the components.