U.S. Navy Designation Help

For Ray Meketa. Ray, I recently acquired a 5in-51 Catapult shell which is so marked. The mouth is perfectly round, but measures exactly 6 3/8 inches inside diameter. Is there any relationship between the 5 inch designation and the fact that the shell ID is 6 3/8 inches ??? Do all USN shells have such a wide discrepancy ??? Thanks, Bill Ballard


Catapault cartridges were waaay before my time so this is all conjecture and WAG on my part.

The 5"/51 was a bag gun, except for a few at the end of it’s life that were seperate loading. I think the seperate cases may have been bottlenecked. If so, a catapault cartridge made from a 5"/51 case would have been cut off and the mouth would have been considerably larger than 5".

How is yours marked? Is it stenciled or stamped? A few measurements would tell a lot. How long is it. What is the rim diameter. Things like that.

Sorry I can’t help more.


A couple of links to expalin its use. And being a cutdown tapered shell would effect “bore” dia., hence the 6"+ reading.



flightglobal.com/pdfarchive/ … 01162.html

Great info, Rick! That has to be one of the larger "CAD"s used for sure…Would guess there’s not too many of those cases kicking around anymore.

Here’s a pic of the USS Mississippi where you can see the catapults.
en.wikipedia.org/wiki/File:USSMi … iBB-41.jpg


Ray, the case is 33 inches long and is straight. The rim is 7 1/4 inches in diameter and 9/16 in. thick with about a 3/8 inch wide bevel. The case is stenciled on the side “CATAPULT AMMUNITION”, “PRIMER MK14-1TS-39 IGN CHG 300 GRAMS”, “BLACK CANNON POWDER CHG 21.75 LBS. S.P.D. 3595”, “BEFORE LOADING IN GUN REMOVE MOUTH PLUG CARDBOARD DISTANCE PIECE & WOOD DISC”. The head is stamped " 5-IN-51 CAL MK-3 CATAPULT NS- 1942 J.C.A. LOT 58". I don’t have a scale big enough to weigh it, but I would guess about 25 pounds. Hope this helps. By the way if someone could tell me where to find a photo of a true 5-in-51 shell case, I would appreciate it. Thanks, Bill

Thanks, Rick. They are good links. I am in the same category as Ray – waaay before my time. Bill


That’s a big one at 33" long! I had pictured in my mind (for no good reason) something about half that length. I would think that would win most bets you get into for “Largest CAD Cartridge” competitions! 21.75 lbs. of chunky black powder burned off at relatively low pressure must’ve been a real treat to clean up after! Great item and thanks for the detailed info on the markings.



That’s a new one for me. I agree with Dave - the mother of all Impulse Cartridges! It looks like you found yourself something special.

I don’t think I’ve ever seen one of the 5"/51 seperate loading cases. Some of our Big Ordnance guys must know what they look like.


Some tidbits.

First, the 5" 51. Still haven’t located pics.


The specs match yours, mostly.

And this, about when they started using this system.
From the NY Times, Oct. 17, 1921.

query.nytimes.com/mem/archive-fr … 838A639EDE

All this might help narrow the search criteria for those that are interested.

Thanks to everyone. I now know more than I thought I would ever find out. Regards, Bill


Your case dimensions are correct. This is not a cut down.
A few years ago I saw a headstamp pict wich I show.
Could you please post some pictures of your case?

Thanks in advance,

Western, I do have photographs, but do not know how to use Photobucket yet. If some kind person will send me an email to wd.ballard@pvco.net I will send them to them for posting. Thanks. Bill

Bill , thank you so much for sharing your pictures!
This is a rare case and the ink stamps makes it a very nice piece.

Thank you Rein for posting the pictures. Some day I may have time to learn how to do it myself. Regards, Bill


That’s a great case and I would dare say a very desirable one at that! Thank you for sharing the info and images.