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Medium caliber U.S. Navy from the O'Brien room


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Premium Member
I've been moving and rearranging things recently and had room to take a few photos of some U.S. Navy Projos and rounds.

Photo one 5 inch 40 cal 1893, 4 inch 40 cal 1897, 4 inch 50 cal

Photo two 4 inch 50 cal, WWI through WWII, the tallest round 50 inches long.

Photo three 5 inch 25 cal Submarine gun, 3 inch 70 cal

Photos four and five 5 inch 38 cal separate loading.


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More U.S. Navy Medium Caliber Projos

Photo one 5 inch 54 cal WWII and current paint schemes. The middle projo is made in two halves, and is assembled by having the bursting charge inserted in a prepackaged sausage shape. The two halves are forced together with an interference fit. It has no rotating band, but instead has a plastic obturator/driving seal that is press fit on the base. The knurling can be seen on the projo to engage the obturator. Projo is a Hi-Frag alloy designed for the rapid fire automatic gun. These halves were factory rejects and were never assembled or painted, vintage 1989. The fuze protector is designed to be removed automatically by the gun, whereas all of the other shown are designed to be unscrewed by hand.

There are a few Bronze and one bronze painted projos in the photos. Bronze is a color used for loading dummies from projos to bombs and mines. Originall WWII projos were bronze. They typically are without rotating bands, so that they don't engage the rifling and stick in the chamber. More recent dummies are merely painted bronze color and no. 2 in photo one.

Photo two, 6 inch 47 cal, the same projo can be used for HE, WP, Chaff, and Illum. The projo on the right is a APCBC Painted practice colors.

Photo three close-up of WWII paint for Illum projos. The projos are labeled "Special Fireworks"

Photo four is the more modern paint scheme for Navy Illum Projos


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That's what I call a beautifull collection of shells. Especially the 3 inch 70 cal shells. Never seen that type before.
Regards DJH
Very very nice, lets hope you keep moving things around and take more photos.
US navy shells

Very impressive, wish I had a collection like that (but British navy which is my main interest) 2pr
3 inch 70 cal guns


Info on the 3 inch 70 cal gun. The UK had these also, but as a separate loading round. The U.S. round has a threaded rotating band, and the case mouth is threaded to match. I have a UK case, and it has a threaded plug in the case mouth. The projectile also has a forward brass bore-rider ring located at the bourrelet.


The 3 inch 70 cases are cadmium plated steel. The guns were only active from the 1950s through the 1960s. When the U.S. scrapped out the ammo in the 70s, the cases and projos were available from surplus stores. I had one of the cases standing next to my color TV when I was in college, and the case had evidently been moved by a crane with magnet, because the case was magnetized so much that it screwed up the picture on the TV set.


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A fair few escaped over here and were sold off as scrap !


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Thanks for posting your photos. I had forgotten how the UK bore riding band is different than the U.S. one.
U.S. Naval rounds...

Hello John,

That's the best collection of U.S. Naval ammunition I seen! Truly a magnificent grouping of ordnance. I especially like your 1897 4"/40, I've been trying to find one of those for years. Where are your 8"/55's ?

Best regards,




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Thanks! Your 8 inch and 6 inch HE rounds look great! Almost all of my other Navy stuff isn't in a good place to be photographed right now. I actually worked at the factory where the 8 inch 55 cal brass cases were made. The last forming operation squeezed the rim out on the head of the case. It was done on the 6,000 ton press. I was working there when the 5 inch 54 cal Hifrag projos were made. Check the headstamp on your 8 inch case. If it says NIV or NOR, it was made at that factory. If it says NGF, that is the naval gun factory. They were the only other place that had a 6,000 ton press.
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Hi Haz

Nice collection.

Mine resembles your Blue 5in, but someone has cleaned it off except a little bit left under the copper ring.

Can i ask.

1. What type is that.
2. What Adapter and Fuse is on that.
3. know anywhere i can get an adapter and inert fuze from lol.

Many thanks
Years ago there was a place here in the states that had some adaptors, but the guy that ran it is dead now. The proximity fuze is wider and doesn't need an adaptor.

Blue with white lettering can be a practice shell. Blue with a star is the old color code for illuminating. You should be able to ID the projo by the Mk. and Mod numbers on the band.