Army vs. Navy Gun Nomenclature

Does anyone know why Army nomenclature for large guns is usually something like “90mm M1B1” and Navy nomenclature is usually “76mm/62 Cal” or “5 inch/54 Cal”. I know the “62 or 54 Cal” is the length of the tube or barrel as a multiple of the diameter of the projectile. But why the two different systems of naming?


Probably the same reason that a Captain in the Army is a Lieutenant in the Navy. And a Navy Captain is an Army Colonel. And the commander of a ship is a Captain, regardless of rank. :) :)

Even though I have a military mind, one should never try to make sense of anything military.


Ray–I agree that there is no since to much of Military Thinking, but as crazy as it often is, there is usually some history behind it. So, why did the Navy develop the system of using a multiple of the projectile diameter to designate the length of the barrel. I am sure it dates back to muzzle loading cannons and probably has it’s origins in ballistics. But, it seems like a strange thing to derive as a method of designating different guns. The cartridges are, of course, are headstamped for the gun they are used in, so you have a 5 inch/30 Cal. and a 5 inch/54 Cal., but it would seem to make more sense to designate the cartridges 5 inch x Length of the Case. as I am sure the same cartridges are used in more than one model or gun system.

This pretty much sums up the Naval reasoning. Plus some other interesting info.

Slick Rick–That is a GREAT link. Thanks.

The Navy designation includes not only the caliber information (5 inch 54 caliber or 5"/54) but also a Mark and Modification which is the equivalent of the Army M1A1 (M1A2, M2B4, etc) designation. Remember, there is a separate designation given to the ammunition, barrel and entire gun in both the Army and navy systems.

Thus there are separate Marks and Mods of the 5"54 gun mounts, and indeed the barrel themselves, for the original slow fire guns used onthe Midway class Carriers, and the later rapid fire (Mk 42) mounts used on Forrest Sherman (DD-931) and later Destroyers, and the Mk 45 lightweight mounts used on the Spruance (DD-963) and later Destroyers- even though all could use the same 5"/54 projectiles and powder charges.

The Navy was using “Mark and Mod” designations since the late 1800s, while the Army went through Model of [year] before settling on the M1A1 type designations.

The original reasons for adopting the systems must have made sens at the time, but the reason for continuing to use them is much more practical- it is simply to hard to go back and change every technical manual, and all the supply manuals and blueprints which govern contracts for replacment parts as weapons systems typically remain in service for decades after originally adopted, both in U.S. service, and later with allies to whom we often provide logistics support.

To make the Mark and Mod even more confusing - in the early 1900s they were designated by Roman Numerals, thus MK IV - I, and after WWII by numbers, thus MK 4 Mod 1. WWII was the period of changeover when both systems overlapped and were even mixed at times.

On a round of USN ammunition, each part or assembly has it’s own MK and Mod. The case, the projectile and the fuze will all be numbered differently. Add the lot number of manufacture, the bursting charge, tracer color, weight, projectile type, etc etc and there are a whole lot of numbers to keep track of. Fortunately, they are painted and that is really the only thing a Gunners Mate pays any attention to.

What a color-blind Gunners Mate would do, I have no idea. I never met one. Make them Yeomen, I suppose. :) :) Is color-blindness still a reason for military service rejection??

Somewhere, I have the projectile color codes pre WWII, if anyone is interested.


Ray–See my post a little while ago for a chart of the paint schemes for Navy projectiles.

This is even more specific. … lature.htm

Re: Ray’s question about color blindness.

It is not a disqualifier for entry. It does limit career options. Not sure as I would WANT to be a color blind EOD tech.


Now that I think about it, there are some ratings where it would be downright dangerous to be color blind. Gunners Mate, EOD, Fire Control, Electrician, Airdale, Signalman, Radarman, Ordnanceman, are just a few that come to mind.


And by the way. Some of my best friends were Yeomen. Snerk


I’ve nothing against Yeomen. I’ve had many a beer with them. We were all Shipmates. I meant that they could do their job whether color blind or not. Everything was black and white.

What’s a snerk??


Just a joke. SNERK = Snide(smart a$$ed) remark. I wouldn’t worry too much about offending any Yeomen on this forum, what with their being illiterate and all. JUST A JOKE! I’M JOKIN"!!!