Fightlite Industries MCR Main Action Spring Features The Fightlite Industries MCR Main Action Spring is manufactured from steel and designed specifically for belt-fed MCR rifles and upper receiver assemblies chambered in .223 Rem and 5.56 NATO. As the main action spring it stores and releases the energy that drives the bolt carrier group rearward and forward through each firing cycle directly governing reliable feeding extraction and ejection. A belt-fed action places repeated compression cycles on this spring at a faster pace than a standard magazine-fed rifle so its steel construction is built to resist fatigue over extended use. Keeping this spring in good condition is central to the MCR system cycling correctly under sustained fire. Fightlite Industries built this spring as a direct factory replacement part matched to the exact specifications of the MCR platform rather than a generic AR-pattern spring. Routine replacement of the main action spring is a standard maintenance step for belt-fed shooters who want to avoid short-stroking or failures to eject as a factory spring ages. Installing a fresh spring restores consistent cycling force without requiring any other parts replacement. This part is intended for MCR owners performing scheduled maintenance or troubleshooting a rifle that has started to run sluggishly. FightLite Industries MCR Main Action Spring Specifications Manufacturer: FightLite Industries Model: MCR Main Action Spring Caliber: .223 Rem / 5.56 NATO Material: Steel Compatible Hosts: Fightlite MCR Rifles Available At: GrabAGun