That’s some serious range! How do you convert between caliber and mm?
58 caliber means that the length of the barrel is 58 times the diameter of the projectile. Therefore, 58 x 155 mm = 8.99 m (29.49 ft).
In this case, caliber refers to how many times the barrel is longer than the diameter of the projectile.
The projectile has a diameter of 155 mm (6.1 inches), so a 58 caliber barrel would be 8.99 meters long, or 29.4 feet long.