sentences:  Within each turret, a red stripe on the interior wall, inches from the railing, marked the boundary of the barrel's recoil, warning the crew to keep back.When brought into service during World War II the guns had a barrel life of roughly 290 rounds, limited in large part by the nitrated cellulose (NC) propellant.After World War II the Navy switched to smokeless powder diphenylamine (SPD), a cooler-burning propellant, which increased the barrel life from 290 to about 350 rounds.