Firearm attachments, namely, modular external rail systems for firearms; Firearm attachments, namely, modular external rail systems for attaching accessories to firearms; Firearms; Pistols; Pistols and parts thereof; Rifle ammunition; Rifle barrels; Rifles; Rifles and parts thereof; Ammunition for firearms; Combination pistols and rifles; Component parts for pistols; Component parts for rifles; Muzzle brakes that screw onto a rifle barrel