It is a forerunner of the rifle and other longarm firearms. An improved version of the arquebus, the caliver, was introduced in the early 16th century. The word is derived from the English corruption of calibre as this gun was of standard bore, increasing combat effectiveness as troops could load bullets that would fit their guns (before, they would have to modify shot to fit, force it in, or cast their own before the battle). Heavy arquebuses mounted on wagons were called arquebus à croc. These carried a ball of about .