WWII Navy Mark 34 Electric Primer; info needed

A good friend is trying to get information and a couple of specimens of a Mark 34 electric primer used in WWII by the U.S. Navy with big-bore guns, 8 inches and up, and in the Little Boy atomic bomb. The specimens will wind up in a Los Alamos museum. There’s a possibility that it’s not a MK 34, but a MK something else. Whatever, it’s not a Gyrojet, so I’m stumped. Thanks for the help.


Here is a link to some great Navy material:


There is a MK 35 Mod 0 Electric Primer used on 8" Navy cases. Didn’t see a MK 34. Hope this may be of help.


Edited to add: The above link goes to “U.S. Explosive Ordnance” OP 1664 (Vol. 1) dated May 28, 1947 at the beginning of the primer section. The next (2) pages have a (not to scale) picture of several primers including the MK 35 on page 139 and limited specs are on page 140. Page 78 has an index of cartridge cases and indicates the 8" MK1 uses the MK 35 primer. Go to the table of contents to see all the rest. The link is hosted by the Historical Naval Ships Association.

Also added: There is a Mk 15 Mod 1 shown as used in “All Bag Guns”.


If one can believe this Wiki article, the Little Boy bomb used (3) MK 15 Mod 1 primers to fire the gun.


This makes sense with the “8 Inch and Larger” use you indicate as the big ones were bag loaded.

Likely examples are plentiful in collections out there. Good luck with your hunt!


Thanks. The Museum folks said that the Little Boy did use the Mk 15 primers, but they had problems keeping them in place, so switched to the Mk 34 for the next version, and that is what they are looking for to complete a display.

I had already provided them the info from OP1664 cited above, but appreciate your bringing it up.

So, still looking for info on the Mark 34… or better yet an actual example…


Somehow I missed your post on this subject from last night! It is interesting that there was further development of that bomb type (it obviously worked) as there were only 5 built and only held in reserve. The Fat Man type was stockpiled in numbers over 100 from what I understand. That document from 1947 is just about right for time frame but maybe the MK 34 was discontinued before then.

Neat ammunition subject.


Dave; Thanks for the information. John; I didn’t know you were on the same quest for the MK 34. I guess the museum guys put out multiple feelers, which is not a bad idea. I’ll let you know if I find one, and you can do the same.