The term 'biathlon firearm' refers to a RIFLE, which is a type of gun that is designed to be fired from the shoulder. It is commonly used in the sport of biathlon, which combines cross-country skiing and RIFLE shooting. The RIFLE used in biathlon is typically a .22 caliber bolt-action RIFLE, which is lightweight and accurate. The RIFLE must also be equipped with a special scope for shooting at targets from long distances.