37mm USN 1 Pdr


When it comes to big bore stuff I normally plead ignorance. I recently found this USN 1 Pdr case.

Rim 45.0 mm
Base 40.5 mm
Lgt 136.4 mm

I’ve found references to 37x137R USN Heavy 1Pr/MacLean cannon and 37x136R pre-WWI naval Heavy 1 pdr. Am I close?

Also who was W.MFG. CO and what does JBS stand for?


From the draft of my book on cannon and their ammo:

37 x 136R USN 1 Pounder Mk 6, Heavy

This cartridge was originally designed for a manually-loaded Hotchkiss gun which entered USN service in about 1890 and was also used in various other guns and sub-calibre training systems. It was adopted for two automatic weapons in the first few years of the 20th century: an enlarged Maxim "Pom-pom" known as the One Pounder Maxim-Nordenfelt, Heavy, Mk 1 (later designated 1 pdr Mk 6), which during World War 1 was ordered in large numbers for the USN; and another US automatic cannon developed by Samuel N McClean (of Lewis Gun fame). Although the gas-operated McClean gun failed to be adopted by the USA, a sale to Russia (who called it the "Maklen" gun) during World War 1 of just over 200 guns subsequently led to them being widely distributed.

The brass cartridge case was rimmed and slightly bottlenecked. Various projectiles were used, but all seem to have been of the base-fuzed steel pointed type. The overall length of the round was 210 mm and the weight was around 600 g. The standard projectile weight was 476 g and the MV 640 m/s from an L/42.5 barrel.


Great information! Thanks for the reply. Now I’m really looking forward to your book.
Any ideas on the headstamp?


Sorry Paul, headstamps aren’t really my thing. If I had to guess I’d say W might have stood for Winchester, as they did make a different 1 pdr round (37 x 120R) for the Army’s five-barrel Hotchkiss rotary.

Western Front Museum page has a list of headstamps and identifies
WMFG Co as Winchester Manufacturing Company.

This may or may not be correct as the Winchester everyone thinks of was officially Winchester Repeating Arms Company and usually used WRA Co. Winchester did make a variety of artillery shell cases from 37mm up to about 6 inch. The list linked above does NOT include a listing for WRA.

Winchester officially ever had a facility named Winchester Manufacturing Company?

Anybody with images of a Winchester 1918 large caliber headstamp which features “WRA”?

Thanks you all for your input.
I guess the W.MFG. Co is still somewhat a mystery.
What about the “JBS”?


JBS would be the initials of the inspector.

Paul, the manufacturer is Worcester Manufacturing Company, Worcester, Massachusetts. They also made shells, fuze sockets, and shrapnel.