The idea is not so much to pierce or punch a way thru but to 'glide' thru. The materials used are conventional tungsten carbide coated U238 but the shape is different. Everyone is aware of the streamlined 'Tear shape' with a tapering tail ( we are talking discarded sabot here ) now think Narwhal with a very short tusk. The projectile has a high lengh to diameter ratio. On contact the tungston needle pierces into the armour surface then the shoulders of the needle 'tear' the material apart forming an ever penetrating crack. This is important - hard materials that can withstand shear and tension are often susceptable to a tearing deformation. The next stage is vital, the shoulders blend in to the front of the tearshape projectile. This due to the high density 'pushes' the material to the side compressing it ( remember there is a lot of lateral material which can be compressed. ) After the broadest part has passed the elasticity of the compressed material wil make it take up its origional postition, as it does so it will push against the extended tail of the teardrop forcing it forward. Thus the energy used in displacement is returned to the projectle ( of course there are losses. ) Apart from the initial break thru the only real energy demands will be that of the relatively low tearing action. The dense projectile will glide thru the armour like a modern streamlined sub thru water. Of course once it passes thru a turret narrow as it is its effect will be devastating.
