The cap (the “penetrative cap” as the above picture calls it) protects the hardened tip of the shell itself, so that the tip doesn’t deform immediately on impact with armor. Soft metal caps did exist and work, but hard metal caps became more common since the hard cap would survive a little bit longer and thus get the shell better positioned to penetrate by the cap hopefully going through the outer layer of armor before the tip on the shell came forward to penetrate the remaining armor.
![[OC] Projectile ring for ammunition inside the 16 inch main gun of the USS North Carolina](https://lemmy.world/pictrs/image/b54e0d3c-047a-4cd3-b73f-aaaff9c09feb.jpeg){kind=link}
Almost.
The cap (the “penetrative cap” as the above picture calls it) protects the hardened tip of the shell itself, so that the tip doesn’t deform immediately on impact with armor. Soft metal caps did exist and work, but hard metal caps became more common since the hard cap would survive a little bit longer and thus get the shell better positioned to penetrate by the cap hopefully going through the outer layer of armor before the tip on the shell came forward to penetrate the remaining armor.