"Armour Piercing Keris" ???

[Timo Nieminen]

Originally Posted by A. G. Maisey

Pretty well established that it did happen Timo, I have no idea at all of what Dutch breast plate is like, but the fact that Brojoguno keris did penetrate them is a part of history.

Originally Posted by ariel

Don't know about keris, but European estocs were actually designed for stabbing through solid steel cuirasses. Even in the 19th century French cavalry was trained to stab rather than slash, and their opponents wore cuirasses ( not all, of course, but quite a lot). So yes, it was possible. And sticking 2-3 inches of steel inside any part of torso was almost guaranteed to be fatal.

Estocs were not designed for stabbing through steel cuirasses. They're designed to stab in the gaps of a plate armour, and to defeat the armour in the gaps (e.g., mail voiders covering the gaps). The problem with breastplates is that they're designed to keep lance points, pike points, arrows, crossbow bolts etc. out, and perhaps bullets.

I suggest an experiment: get some mild steel sheet, 1.5mm thick, and try to stab through it, with whatever one-handed dagger, knife, or sword you wish to try. That mild steel sheet is better quality (but thinner) than the lowest quality iron used to make cheap munition armours, and if the results in Williams, The Knight and the Blast Furnace, section 9, are good, it's about as protective as a cheap and nasty munition breastplate of 2.5mm thickness, or a mediocre breastplate 2mm thick (2-2.5mm thick is typical, for infantry breastplates).

With a close-to-optimal tip for penetration, you can just penetrate (i.e., make a hole all the way through, but only just) that 1.5mm of mild steel with 80J of energy. Make that about 110J if you want to tip to go through far enough to be effective. This isn't easy to achieve, especially if the target is trying to avoid being stabbed. The best possible armour piercing tip doesn't make it easy (or depending on the breastplate, even possible) to pierce thick iron plate.

Given that some armours will be thinner, will have defects, will have thin spots, etc., the best one-handed stabs delivered by humans, hitting square-on, should be able to occasionally go through (not against much-thicker cavalry breastplates, though). But there are some serious problems with trying that and hoping it will work as a fighting strategy. It's much, much easier to go around the breastplate than to go through it. There's plenty that it doesn't cover.

What an "armour-piercing" tip will give you is a tip that will survive hitting a breastplate when you're trying to go around it. It's also a good tip for piercing chainmail (which was used by the VOC), or against armoured-all-over soldiers, piercing the much thinner armour on the limbs.