Bunny, yes, the "caliber" on any naval rifle or cannon refers to the barrel length...you can roughly conclude the velocity from that too comparing gun to gun...for example while both opposing DDs (say Jap and US) might have 5" guns, or both of their Cruisers might face each other with 6" or 8" guns, the LONGER tubes would give one or the other an advantage in a surface fight with regard to range...so while the 5"/50 cal DD guns from preWWII and the 5"/38s of most WWII DDs fired technically the same shell WEIGHT, the /50s would throw them farther (usually bigger powder capacity) and with more velocity...but then the shorter barreled guns USUALLY had a higher rate of fire, and could be "trained" faster....

But the SHORTER barrel is also needed for high elevation, such as for "dual-purpose" or AA only use, so that is why a lot of WWI and pre-WWII DDs carried "mixed" weaponry, with 4"/50s, or 5"/50s, or maybe even 3"/50s for "surface" targets, and a couple of 3"/(shorter) "high angle" guns that were "AA only." So consequently they had relatively lighter armament than they could have had for BOTH Surface or AA use, and were really pretty light on the AA....plus had to carry two or more types and sizes of shells for the two different "main" guns.

The 5"/38 was perfect for both, with sighting systems and fire control for surface and AA targets, (hence Dual-purpose)and gave the WWII DD and DE the full main battery for A/ship, but all were highly effective for AA too, not even accounting for the new "proximity' fuses and the automatic (actually "semi-auto") rapid fire capability which made them DEADLY.

Interestingly, I have heard that the longer barreled 4" and 5" guns were more accurate than the 5"/38s, but they more than made up for it with the rapid fire, and with proximity fuses, "close" was usually good enough.



If Xracer gets on, he can give you a lot of first-hand experience with them too....

 

If you take the caliber times the bore diminsion, it will give you the barrel length.

For example a 3" 50 cal is 150" long. A 5" 38 cal is 190" long.

A longer barrel allows you to use a higher powder charge, and get more velocity. For instance a 5" 51 cal has a higher velocity than a 5" 38" cal gun.

 

Some savvy naval gunners here, I see.

One aspect of the 5"/38 dual-purpose gun is/was its "throw weight". With its automated systems its ablity to deliver a very high rate of sustained fire compared to more powerful guns of equal caliber made it more effective. Sort of like the difference twixt the '03 and the Garand.

"What's old is new" can be applied to today's navy, as well. In the days of sail, gun drill and the ability to deliver sustained fire over a long period often made the difference over weight of metal. Modern naval guns may be smaller in caliber, but deliver a higher rate of sustained fire over a longer period far more accurately than even fans of the 5" 38s ever dreamed of. >MW

 

And bunnyhunter, the caliber in this case is not expressed as a decimal, as in bore size - it's an integer, a multiplier in this case.

 

Why not just give the bore size and length of barrel? I know the navy has some strange ways of communication (I do understand the reason for port/starboard) but this makes no sense to me.