30 mm case ID


Good day

I have recently picked up a 30 mm semi rimmed case and I have not been able to identify it.

I will try and desribe it as best as I can.

Headstamp (original imprint very light)
C.B. & C. CO. (12 o’clock)
LOT (9 – 8 o’clock)
1649 (6 o’clock – towards outside)
H D H (5 o’clock)
US with anchor (3 o’clock) (US Navy symbol)
At 6 o’clock close to primer socket heavily struck out appears to be 1.10 “ MK – 1
At 6 o’clock in the middle – very faint what looks like – 45 CAL
At 12 o’clock below manufacturers code is 8 – 42
Bold overstamp 30 MM . FX . 10

Case measurements

Case length – 182 mm( appears not to be cut down)
Base diameter – 43.5 mm with bevelled edge
Inside extractor ring diameter – 39.5 mm
Extractor groove depth – 2 mm below head
Case diameter above extractor groove – 41.2 mm
Case length to shoulder – 140 mm
Case diameter at shoulder – 40.2 mm
Distance from shoulder to neck – 30 mm
Length of neck – 12 mm
External diameter of neck – 32 mm
Inside diameter of neck – 30 mm

Primer Socket (non threaded)

Thank You John



I think that you have a case for the 1.1 inch US Navy AA gun. This has been thoroughly discussed in the past on this forum, maybe in the old section. This is not in my area of collecting but there are several IAA members who can help, they are still snoozing just now. The gun was usually mounted in multiple barrel format, four was one variant. You could also try Googling 1.1 inch US Navy AA gun.



There is some good info on the 1.1" 75 cal. here: viewtopic.php?f=1&t=5229&hilit

With the case length being short and the 30mm overstamp, I wonder if this one was used for something else?
Did a quickie with the given dimensions and while I don’t have an unaltered 1.1" at hand, the body taper and shoulder look about the same.(?)
The neck seems to be the only difference being shorter than the normal of a little less than one caliber and its dia. would seem to be a bit large for a fired case.

The over-stamping is the very interesting part!



Dave E

Your picture is spot on, it is interesting that it is stated as being a 28mm projectile. From the pictures i could locate my case may have been cut down as the neck appears shorter, though it is most certainly 30mm as marked on the case???




We’re not worthy!!!


Here’s my example of an unaltered hull.


Slick Rick

What is your take on the 30 mm over stamp on the case ?




A few thoughts while we wait for Rick’s input:

I checked measurements against my 1.10" 75 Cal. example and the body and shoulder lengths match your dimensions. This one has a seated and crimped inert H.E. projectile (complete with inert PDF MK 34 fuze just to make Rick envious) and the neck O.D. measures 29.1mm. If not for the interesting over-stamp, I would say yours was a damaged case mouth of a fired case trimmed back to look better and perhaps the 30mm I.D. is from a straightening effort.

I have seen pictures of the same case necked down to 20mm for some experimental purpose but don’t know if these were re-marked as far as the headstamp. It would be possible I would guess that experiments were done necking this case up to 30mm. I hope we can hear of this having been done as it would be new to me and would make your case a very interesting find!




Not a clue whether these (1.1" 75 cal) were experimented with. If so, as in your sample, then I would be very proud to have that particular hull. Even if it did not contain a H.E. projectile (complete with inert PDF MK 34 fuze.

The other option, just somebody cleaning up a bent up round, well, maybe so. Neat, regardless.

A pic of the headstamp would be a nice addition to the thread.



High-velocity projectile testing, probably. There was also a 23mm version of the case for one of the .90" guns being played with around 1940-41 (other versions had smaller cases).

Yes, it would! The best guess I can make would be for initial projectile testing when the US was considering the merits of a 30mm gun but before they’d built any - perhaps the programme that led to the GAU-8/A?


I Hope this is how you post a photo ? First timer

s928.photobucket.com/albums/ad12 … G_8598.jpg



You can get the picture to post direcetly by posting the IMG code.

As they are, I can see them going to you photobucket album and I would say you have a real neat item there!

There looks to be a strike-out across the 1.10" designation as well. A very interesting case that may well be some 30mm developmental like what Tony Williams suggests and as such I would think quite rare. Great find and I hope we can learn more about it some day!



Here’s John’s headstamp.

And the shorter neck.


I’d say that’s a mighty fine and rare example.

Bettin’ DaveE would trade his H.E. projectile (complete with inert PDF MK 34 fuze. for that.



The first of those I get for trading will be available for collectors in Arkansas only…Just haven’t seen any others yet.




Muchos gracias, amigo. My hull feels so, well, empty.

Had the pleasure of skyping with John. To offer picture posting hints. An amazing thing, these computers. It’s about 1530hrs, tomorrow, in Australia, as I type this, in case anybody wanted to know that.


Really nice case, where did you find it?


John, you read the headstamp " Bold overstamp 30 MM . FX . 10 "
I would say it is " 30MM. EX. 1-0 "
Hope this can help to find out more about this very interesting one.


Hi Falcon

I picked it up last weekend at a local flea market. Nothing like treasure in the trash.



I find quite a few artillery cases at flea markets or “car boot sales” as we call them in the UK. It is surprising what can turn up.