In general, rifle muskets were the same length as the smoothbore muskets they replaced. This meant that they typically had a barrel length of about and an overall length of about . Period U.S. Armory nomenclature described rifles and rifle-muskets as newly made firearms specifically designed and manufactured with rifling. Rifled muskets were smoothbore firearms returned to the armory or contractors for rifling. Considerable numbers of armory-stored smoothbores were converted in this way in the 1850s upon adoption of the Minié ball as the standard projectile. Rifle muskets tended to be of smaller caliber than their smoothbore predecessors, for example, the .58 caliber U.S. Springfield Model 1855 or the .577 caliber British Pattern 1853 Enfield. Tests conducted by the U.S. Army in the mid-1850s showed that the smaller caliber was more accurate at longer ranges. The cylindro-conical shape of the Minié ball also meant that the smaller-diameter but longer .58 caliber Minié ball had roughly the same amount of lead and weight as the larger .69 round ball. While the caliber was reduced, the overall length of the barrel was not. Shorter rifles could have easily been made (and were made for specific branches or arms such as mounted infantry and riflemen) that would have been more accurate than the smoothbore muskets they replaced, but military commanders still used tactics like firing by ranks, and feared that with a shorter weapon the soldiers in the rear ranks might accidentally shoot the front rank soldiers in the back of the head. Military commanders at the time also believed that bayonet fighting would continue to be important in battles, which also influenced the decision to retain existing barrel lengths.