Provided is a trigger group module for a firearm that includes a portion defining a trigger group receiving area having laterally spaced apart walls with at least two pairs of laterally opposed openings for receiving assembly pins. The trigger group module includes a module frame sized to be inserted into the trigger group receiving area and has assembly pin receiving openings positioned to align with the laterally opposed openings in the walls of the trigger group receiving area. A hammer member is pivotally supported by the module frame along a first substantially transverse axis. A trigger member is supported by the module frame along a second substantially transverse axis. At least one of the first and second substantially transverse axes is not coaxially aligned with an assembly pin receiving opening.