HK 416 Firing Pin Retaining Pin - Factory Original This genuine Heckler & Koch firing pin retaining pin is made from durable steel and manufactured in Germany to exacting standards. Designed for HK416 rifles chambered in .223 Rem / 5.56x45mm, as well as compatible AR-15 platforms, the captive pin secures the firing pin in the bolt carrier group. As with all H&K components, this part reflects the brand's reputation for precision engineering and premium quality.