Heckler And Koch MP5 9mm Ejector. Constructed from black finished steel, this factory original part from H&K is made in Germany and designed for HK MP5 rifle models chambered in 9mm. The ejector, located within the trigger mechanism, is responsible for ejecting spent cartridges from the fired weapon. Heckler & Koch is world renowned for their high quality firearms and parts. When you buy an H&K part or accessory, you know that you're getting the highest quality materials and assembly available.