WMD Guns AR-15 Firing Pin 5.56 NiB-X Nickel. 56 (NATO) firing pin is a standard firing pin that functions as a standard firing pin. The 5.56 (NATO) firing pin has a slightly larger diameter and a "bucket" shape that allows it to fit into a magazine more easily. The charging handle is a familiar stubby shape that many users prefer as it doesn't require a large amount of room for error when firing. This firing pin has been treated with Nickel by a special company to which all NiB-X firing pins will be sold. The nickel firing pin can be snagged from your magazine fairly easily. If you are looking to convert your 5.56 rifle to another caliber please see our dedicated 5.56 threaded firing pin threaded section. Also make sure to see our dedicated 5.56 threaded firing pin thread section. Specifications for WMD Guns 5.56 NiB-X Firing Pin: Manufacturer: WMD Guns Color: Nickel Caliber: 5.56x45mm NATO Gun Model: AR-15 Package Contents: WMD Guns 5.56 NiB-X Firing Pin What firearm models does the manufacturer say WMD Guns 5.56 NiB-X Firing Pin is compatible with? The manufacturer suggests that WMD Guns 5.56 NiB-X Firing Pin is compatible with AR-15WMD Guns 1-NIBXFP: AR-15 Firing Pin 5.56 NiB-X Nickel