An internal combustion engine and method of operating an engine is provided. The engine comprises a piston cylinder formed within an engine block, an engine head secured to the engine block, a primary piston configured to slide within the piston cylinder, a main combustion chamber that is defined by the primary piston, piston cylinder, and engine head, a variable volume prechamber formed within the engine head and in fluid communication with the main combustion chamber, an ignition device configured to ignite a fuel within the prechamber, and a prechamber piston configured to translate within the prechamber. Translation of the prechamber piston within the prechamber varies the volume within the prechamber. The engine is characterized in that the prechamber comprises at least one orifice that provides fluid communication between the prechamber and the main combustion chamber.