XP & Cavitation
 

Dutch on another forum posted this information about Cavitation or Supercavitation. He was kind to try to explain to me the theory of Operation of the new Lehigh XP bullets.

As noted in an earlier post the penetration is enhanced by the flat surface on the front on the bullet. The mechanism is called super cavitation. A typical flat point bullet will have a round, flat meplat. If the meplat is a large enough diameter it will create a vapor bubble that will be large enough to form a cavity around the body of the bullet. This vapor cavity effectively eliminates all drag that would be produced by the target medium (liquid and remember flesh is mostly water so this applies to the chest cavity of a game animal). The only drag is from the meplat itself. This is why non-deforming, flat pointed bullets always penetrate further in a liquid medium than do non-deforming sharp pointed bullets. It seems counter intuitive at first but it really is true.

When looking at the "x" shaped damage created by this bullet in ballistic gel, I think we are seeing two things. First the extreme penetration of the bullet is a certain indication that super cavitation is in play here. The "x" shaped wounds look to me to be the result of shock waves emanating from the arms of the X as the bullets travels through the gel.

One other thing to point out is the super cavitation only works in a dense medium like water, ballistic gel, or animal flesh. Pointed bullets are much better in air. Penetration in air is measured in thousands of yards! The military calls it maximum effective range and spitzers have a much longer MER than do blunt bullets.

There was a article several years ago in Scientific American magazine about super cavitation. It seems the Russians developed a 300 mph torpedo! It has a rocket motor instead of screw and a hardened flat meplat to generate the vapor cavity around the body of the torpedo. Thank goodness they never figured out a way to steer or guide the torpedo because there were no fins or rudders in the water to turn it. Had they found a solution it might have instantaneously obsoleted our submarine fleet.

Thank you Dutch

Cool. I heard about that torpedo, I think there was also talk about developing a super fast sub based on the same principal.

Cool. I didn't realize the XP bullet uses the same principles of supercavitation. I had heard about the torpedo, though. It is actually in service with the Russkies- called the VA-111 Shkval. It has a pretty short range, though, and I'm not sure how it is guided. The old versions used inertial guidance and had a nuclear warhead (accuracy by kilotonnage), but the new versions have a conventional warhead. Seems like it would be hard to guide it to hit anything....