Google doesn’t want to give me an answer and I really want to know. Thanks!
In: Engineering
It depends. There are lots of different designs that make a round better at penetrating armor. They vary depending on the size of the round, the cost of the round and the type of gun and type of armor. In general armor piercing rounds are heavier but narrower. This helps put as much energy into a tiny area as possible. For example a 105mm armor piecing tank round might only be 50mm in diameter but made out of depleted uranium or tungsten. The tip of the round is also hardened and might even have a cap which help break up the armor before the main body of the round hits it.
Then there are shaped charges which work completely differently. Instead of relying on mass and speed to concentrate the energy it have an explosive charge that is aimed at a single point. By focusing the blast at a tiny point on the armor it can destroy the armor in that spot and do damage to the inside.
There are lots of other techniques which can be used to make armor piercing rounds. If you look up the available ammunition for any particular gun you will see a list of different armor piercing rounds. The term is a generalization of these types, often used for practical reasons while in the field.
In short, it’s harder.
To elaborate, APBs have a light casing (usually copper/aluminium) which breaks upon impact, allowing the “penetrator” inside to continue forward with force.
These penetrators are usually made of some form of hardened steel, tungsten-carbide, or other similarly tough material; allowing for greater penetration following the impact of the light casing.
Armour piercing shells (APS), as opposed to armour piercing bullets (APB), are used to penetrate and then *detonate* through various methods.
The answer to your question is “Yes”.
Yes, the penetrator (the bit that actually goes through, the round isn’t uniform) has to be harder than the armor to get through. Otherwise it will just deform on impact without punching a hole.
But also yes, speed matters. Materials don’t behave the same when impacting at slow vs. high speeds. The higher the speed, cleaner the penetration will be, as the material doesn’t have time to react to the impact properly. You’re literally hitting it faster than it can “notice”.
There’s many different kinds of AP projectile. For large bores and thick armor (tanks), traditional AP was done using shaped charges. These use explosives to fire a jet of extremely fast metal into the target. This is a HEAT head.
While not technically AP, squash heads work very differently and serve a similar purpose to HEAT. They are designed to create a pancake of high explosive pressed against the armor, and when this explodes it sends shards of the armor flying around the inside.
Small arms typically rely on cored ammunition. Regular bullets with hard cores. The cheap stuff uses steel, higher end ones use tungsten or carbide or even depleted uranium as these materials are much denser than steel. Density is key here.
Modern tank doctrine has shifted to kinetic penetrators. APDS. These are long, dense rods that move super fast. Tungsten or depleted uranium. They use a plastic case to fill up the rest of the barrel bore, since the rods are relatively thin, and this allows great speed. The speed allows the density to work its magic, but without a dense projectile the whole thing would be much less effective.
If you’re firing bullets at something soft (like meat) you want them to squish or break up so they transfer their energy into the target and make a big hole instead of staying together and zipping straight through leaving a little hole.
If you’re trying to get through something hard you want a bullet that doesn’t squish so that all that energy is concentrated in a very small place and hopefully will punch through it.
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