Positioning of penetrator in armour-piercing, high explosive, incendiary round

Here is a nice little schematic of an armour-piercing, high explosive, incendiary round (the Raufoss Mk 211).

Not only is the penetrator in the back half of the round, but both the high explosive and the incendiary components are forward of it. To me, who knows nothing about such things, I would have expected the opposite arrangement with penetrator the most forward component of the three. In other words, I would have assumed that the penetrator penetrates and the explosive and incendiary follow through the opening so made. Clearly my intuition is wrong.

What is the rationale for the arrangement pictured in the link? Is the idea that the HE and incendiary components are slowed down or stopped by the target whereas the penetrator just keeps going, i.e. the penetrator travels past the slowed/stopped HE and incendiary parts, makes a hole, through which the HE and incendiary then enter?


I know next to nothing about such things, but I’m assuming that the penetrator will will draw the burny stuff into the hole that it made, much like the slipstream behind a semi.

That particular round may just be intended to be dual purpose. Fire at some soldiers, and the explosion will pepper them with shrapnel. It might set off ammunition and fuel with a sympathetic explosion. Aim at an armored vehicle with light enough armor (not a Bradley or another APC, something lighter) and the round will pierce it and possibly harm something. They haven’t managed to make wearable armor that can stop a plain lead 0.50 round, so a direct hit on a soldier would obviously severely injure or kill them.

Just follow your link to HEIAP. The explosive starts blasting open the target and the hardened penetrator follows through from kinetic energy.

As a SWAG, you want the heaviest stuff in the bullet at the back so the shock of firing doesn’t crush the explody stuff. If the penetrator was at the front of the round, it would have a tendency to resist the launching force, pinching the explosive material behind it. For something that is supposed to explode on impact, you would want the pinching to happen at the target and not in the barrel of the gun.

Early artillery fuses actually used that principle to start the time delay, a firing pin would be driven back (set back) into the priming pellet when the shell was fired.


That was my thinking; dual purpose, with the HE and incendiary effects for soft targets, and the AP effect for the harder ones. There’s no intention to have behind the armor effects, save maybe having that penetrator rattling around inside after it penetrates, or you’d have something like a tracer on the back side of the penetrator.

The idea that the HE “blasts a path” is bunk; if the HE could blast a path, there would be no need for the penetrator in the first place.

An example of how it would be used would be for a sniper to shoot a car or truck with it- it would set the thing on fire if it hit something flammable, and possibly blow a bigger hole in it while it set it on fire, and the penetrator would continue to penetrate after the HE detonated, doing even more damage. But if he saw an armored car or something like that, he might take a shot at that as well, in the hopes that he could damage the engine with the penetrator. But a 50 BMG round with an explosive charge the size of a small gumball isn’t going to poke a hole in real armor with that HE effect.

It would be

I agree. Those up armored humvees that American forces used in Iraq for a period? The penetrator on a raufoss would probably go through the window of one of those, maybe the side armor. Other country’s have light armored vehicles with similar levels of armor. Or, we might end up facing ISIS armed with something equivalent - I really hope not.

Oh, it might also be effective against attack helicopters. The armor on those can’t be very thick.

My thought was that it was arranged that way to have he proper weight distribution for optimal flight and accuracy. Maybe it isnt’ the best arrangement for the desired effects, but engineering is about tradeoffs.

I want to amend my earlier comment- there’s some consideration of behind the armor effects, in that it’s likely that burning zirconium dust would get drawn in with the penetrator. But that’s a secondary effect, and not what the round is relying on for its main effect.

My guess is that the zirconium dust is intended to be something that burns really hot and gets scattered easily, as opposed to the impact-ignited incendiary compound in the nose of the bullet.