Complex sentence: To prevent corrosion and mechanical problems, the turret is rendered water-tight by rubber joints; the gun itself is sealed by a rubber muzzle plug, which can be shot trough in case of emergency.
Split into simpler sentences: To prevent corrosion and mechanical problems, the turret is made water-tight by rubber joints. The gun itself is sealed by a rubber muzzle plug, which can be shot through in case of emergency.