50 caliber bullet cartridge pen - Texas Gift. This .50 caliber bullet cartridge pen will make a great gift for any outdoorsman or a military enthusiast. First developed for the Browning, a .50 caliber machine gun in the late 1910's, the cartridge used in this kit is commonly used in the military. Utilizing an authentic .50 caliber once-fired brass cartridge and a Cross style ballpoint mechanism.Overall size of the bullet pen is 5-1/2" to 6-3/8". Hand made in Texas. Uses standard Cross re-fill. Price includes free shipping.