Big angry steel slug

This nasty-looking beast was found in a 60+ piece collection of antique and vintage shotshells. It’s solid steel and appears to be lathe-turned, at least in part. It’s big, just a hair under 20 mm diameter and 42 mm long, and weighs 69.1 grams.

What kind of beastie is this? Large detail photos at the link below.

CLICK HERE for more detail photos.

This is the core/base section of a 20x102 API projectile. The driving band and the ballistic cap are missing. The cap was large in order to retain the quite huge incendiary composition.

As I am thinking about it it might be also from a 20x110 USN.
Can’t find my docs on that one, having too many is a curse…

EOD - Can you put all that into “ammo for dummies” English?

20mm (bullet diameter) by 102mm (case length)
Armor Piercing Incendiary designed to break through armor plate, and to ignite spilled fuels and other flammables
Projectile IE: the part that comes out the business end of the barrel
Driving band, a copper ring that engaged the rifling inside the barrel, to spin the projectile
Ballistic Cap / Wind Cap a thin metal cover, used to reduce the wind resistance. IOW a aerodynamic cover

The one on the left (blue projectile) is close to what yours looked like at one time (blue indicates a target practice loading). You can see the driving band below the white lettering and above the brass case

Alex, you are right, it does look like the core/base of a Mk 13 Mod 0 API projectile for the 20 mm Mk 107 Mod 0 USN cartridge.

Thanks Tailgunner and Fede!

So, the “bullet” component I have is the armor-piercing part of the equation?

what is the plinking round at the far right in your picture?

2 bore Hubble prototype. Case by Ed, bullet by me. It’s based on the cannon round next to it.

City dweller
That would be correct

Just found the diagram of another variant of this one:

EOD - Wow, that’s it exactly. What an interesting thing to find in a pile of old shotshells.

Right, ammo is a never ending field of interetsing things…