No headstamp 13.2x99mm Hotchkiss


#1

I’ve had this old, empty .50 BMG lying around for years. I’m sure it’s probably common as dirt, but I am curious as to what country it came from. There is no heastamp, and it is berdan primed (one small off-center hole inside). The firing pin indentation seems odd also. Anyone know? Thank you.


#2

Sure it’s not a Japanese 13mm Hotchkiss?


#3

You know, I just assumed it was a .50 BMG because it looks like one. How close is the Japanese round dimensionally?

Dimensions on this one:
rim: .796"
base: .792"
length: 3.902"
neck OD: .575"
These dimensions are all within a few thousandths of the BMG rounds I have. The shoulder does look slightly forward compared to the USGI brass, but it’s a bit dented so it’s hard to tell. Actually on second look, the neck is definitely about .1" forward.

Japanese would make sense, given the lack of headstamp. I just did a search and found some info on the 13.2x99mm Hotchkiss but otherwise I’m completely unfamiliar with it. I found:

“This weapon used a modified version of the American .50 calibre ammunition, loaded with bullets of slightly larger diameter – 13.2mm as opposed to the original 12.7mm; the cartridge cases were about the same, save for the larger diameter of the neck of the French load.”

and:

“Japan, among others, was so impressed with these weapons that it acquired a manufacturing licence and built 13.2mm machine guns in significant numbers.”

I’m assuming that you are correct. Are these uncommon rounds?


#4

While not exactly scarce, they are not that common. Good find if you don’t have an example. Most I’ve seen have been fired or inerted.


#5

This cartridge was used by the Japanese navy, who also produced Browning machine guns to use it as an aircraft gun. Jack


#6

Thanks guys. It will go in my collection. I’ve had it for years and didn’t have a clue. I think it may have been in with the short belt of fired .50s I got when my grandfather passed away. I think he had told me he brought them back with him from Japan in '45.


#7

Naval 13,2 Hotchkiss (for Shipnoard AA Guns) is headstamped with a Kana symboil for the Naval Arsenal of production, the quadrimester od the year in Roman/ Japanese and the year in Japanese Calendar (two digits) ( Just like Japanese Naval 7,7x56R. very late war production may Not be headstamped.

Army AA ammo is Not headstamped at all ( single and three barrelled Gun arrangements.)

AS to the Naval use of 13,2 in Aircraft Guns of a Browning design, I am unaware that this Occurred…do you have a Japanese designation for the Gun, such as a “Ho” number? ( such guns were considered “Cannon” and not MGs.)

I have a 12,7x81SR Cannon which IS a Browning Copy ( They also made a Browning Copy in 20mm (20x80 RB).

I have one Japanese Naval Hotchkiss case from New Guinea; it was initially mis-identified as a .50 cal, until the Japanese headstamp was cleaned up and decifered. ( “yo” III 99 ( Yokosuka Naval Yard, 3rd Quadrimester, 1939)

With an Un-Headstamped case, the severe Ringed primer is the ID feature ( the US didn’t go over to a ringed .50 Primewr till after the late 1950s, and US cases are headstamped.)

Nice Find, regards,
Doc AV
AV Ballistics.


#8

Doc: I believe the designation of the JNAF aircraft Browning for the 13.2 Hotchkiss round is type 3 (1943); late subtypes of the A6M5 Zero carried three of these weapons in addition to a pair of Oerlikon 20m/m cannon. There was also a JAAF Browning for the 12.7/.5 Vickers-type cartridge. I’m not sure of the designation of this latter weapon, and I believe it was somewhat smaller overall than the naval type 3. Jack