Directly from their website.
The flutes in the nose of the ARX® bullet harness the gain in kinetic energy accrued due to the increased velocity of fluid through the constriction designed into those flutes. Fluid passing through the ARX® flutes travels between one-and-a-half to two-times the velocity of the bullet. A 9mm ARX® bullet traveling at 1,500 fps will result in fluid flowing through the ARX® flutes at nearly 3,000 fps, resulting in a wound cavity in soft tissue that has been compared by some to be similar to that of a .223 75 gr BTHP. In soft tissue, the ARX® is designed to penetrate 12” to 14”, every time.
IMHO we are regressing again in our scientific understanding of wound ballistics. This seems to happen every few years. The last time I think was the RBCD/Le Mas debacle. In this case I think the issue is not what the ammunition is made of, but the claims made by the manufacturer.
Dr. Gary Roberts
The tissue surrounding the permanent cavity is briefly pushed laterally aside as it is centrifugally driven radially outward by the projectile’s passage. The empty space normally occupied by the momentarily displaced tissue surrounding the wound track, is called the temporary cavity. The temporary cavity quickly subsides as the elastic recoil of the stretched tissue returns it towards the wound track. The tissue that was stretched by the temporary cavity may be injured and is analogous to an area of blunt trauma surrounding the permanent crush cavity. The degree of injury produced by temporary cavitation is quite variable, erratic, and highly dependent on anatomic and physiologic considerations. Many flexible, elastic soft tissues such as muscle, bowel wall, skin, blood vessels, and empty hollow organs are good energy absorbers and are highly resistant to the blunt trauma and contusion caused by the stretch of temporary cavitation. Inelastic tissues such as the liver, kidney, spleen, pancreas, brain, and completely full fluid or gas filled hollow organs, such as the bladder, are highly susceptible to severe permanent splitting, tearing, and rupture due to temporary cavitation insults. Projectiles are traveling at their maximum velocity when they initially strike and then slow as they travel through tissue. In spite of this, the maximum temporary cavity is not always found at the surface where the projectile is at its highest velocity, but often deeper in the tissue after it has slowed considerably. The maximum temporary cavitation is usually coincidental with that of maximum bullet yaw, deformation, or fragmentation, but not necessarily maximum projectile velocity.
And
Projectile fragmentation in tissue can also greatly increase the permanent cavity size. When a bullet fragments in tissue, each of the multiple fragments spreads out radially from the main wound track, cutting its own path through tissue. This fragmentation acts synergistically with the stretch of temporary cavitation. The multiply perforated tissue loses its elasticity and is unable to absorb stretching that would ordinarily be tolerated by intact tissue. The temporary cavitation displacement of tissue, which occurs following the passage of the projectile, stretches this weakened tissue and can grossly disrupt its integrity, tearing and detaching pieces of tissue. Note that handgun bullets, regardless of whether they are fired from pistols or SMG’s, do not generally exhibit the fragmentation effects produced by rifle bullets. If handgun bullets do fragment, the bullet fragments are usually found within 1 cm of the permanent cavity; wound severity is usually decreased by the fragmentation since the bullet mass is reduced, causing a smaller permanent crush cavity.
