Anyone have a guess what to use as a starting load....?

[Doc_Stihl]

That's a 9mm for comparison. The neck measures 3".

[edler7]

Once you find primers, it's all downhill from there.

I'd really like to see a pic of the dies and press.

[Doc_Stihl]

Threaded primer of some sort....

I'm thinking a lee hand kit might be my best bet...
Now for a mold....
3" - maybe 12" long??? That's ~30lbs. I might need a bigger pot too.

[Jim Flinchbaugh]

Fill it to the neck with holy black and stuff a chunk o lead in it

[Jim Flinchbaugh]

or make a shot capsule for it and shoot down the forthcoming drones

[captaint]

I like the shot capsule idea best. Maybe 50 cal balls. That oughta work !! Mike

[runfiverun]

i think you need a 45/70 case of black powder to set that off.
i once seen a 35 gallon barell marked 'powder for artillery cartridges',the grains were a bit on the large side.

[DLCTEX]

You don't measure powder for that in grains, but pounds! I'm not pulling the trigger on that in a hand held gun.

[RayinNH]

Good grief. I didn't even see the 9mm until I clicked on the picture to get a better look see. On my notebbok computer it just looks like a .303 Brit casing. I'd double up on the plugs and muffs...Ray

[Chihuahua Floyd]

Can you say hydraulic reloading press. I've seen video a few years back with a log splitter turned reloading press.
My advice, mine the berm afterward. Might want to cast those out of zinc.
CF

[Jim Flinchbaugh]

My advice, mine the berm afterward.
CF

I bet there will be parts of the berm that haven't seen daylight in YEARS!

[DrCaveman]

10 grains of unique, right?

Or maybe 10,000 grains

[shooter93]

Whatever powder you choose...you're going to need a coal shovel.

[10x]

Threaded primer, that may well be an electric primer for a naval shell. Shells are shipped empty and unprimed, and the projectile is shipped separately.
Powder is held in bags that are loaded into the shell casing on the ship and the projectile. (solid, flare, shrapnel, Willie Pete, or H.E.) This simplified storage and made the 3" guns a great deal more versatile. I have no idea if they re-sized the casings, simply reloaded them, or sent them back to the foundry. I got this from a friend who served in the Canadian navy on a destroyer.

[WILCO]

The original "Big Game" cartridge!

[Idaho Mule]

I would start with a 50 lb. sack of black, if that didn't fill it then open up another. We could get a muffler off of a big Cat generator to use as a silencer so no one would here it and then go hunting Sasquatches. I think it would be fun. JW Does anyone got a mould big enogh for this?? JW

[slim1836]

Build a cannon out of it.

Slim

[tmax64]

I'm thinking fill it full of Trail Boss and light her off From a safe distance.

[Wayne Smith]

75mm Howitzer cartridge - jeep towed howitzer. Retired around 1975?? Just guessing.

[cdet69]

Trail boss. A whole lot of it!