[Hatband]

How does “52 calber” relate to 155mm? 155mm @25.4mm per inch is 6.1 inches. A .50 caliber is one half inch so what is “52 caliber”?

[CatoRenasci]

In speaking of artillery (as opposed to small arms) ‘caliber’ has a different meaning than the ‘bore diameter’: it is the number of times the gun tube (past the chamber) is the length of the bore. To put it in simple terms, think of a 6” (155mm) gun or howitzer (guns are typically longer tubes than howitzers and fire a flatter trajectory to a longer range and tend to have fairly small deflection probable errors and large range probable errors - howitzers fire a higher trajectory a shorter distance (good for going over obstacles) and tend to have greater deflection probable errors, but smaller range probable errors, but back to our 6” gun/howitzer...) A 6” howizter with a 25 caliber tube will have a tube that is 12.5 feet long, a 6” gun with a 52 caliber tube will have a 26 foot long tube.

[GSlob]

155mmx52calibers=8060mm [8m] barrel length

[Centurion2000]

At a guess the two most common arty rounds are the 155mm US NATO round and the 152mm Soviet caliber.

Google 152mm artillery, would you like to know more? :)