I had to watch numerous videos to get a good sense of the ins and outs of this new ammo. Things that aren't obvious at first glance:
- If one or two of the 3 portions of the projectile hit the target, the portions which missed will break free of the tether (which holds them together during flight) but in doing so they are drawn back on line with the original aiming point (i.e., there is an inward force exerted by the tether). They claim that will result in the portions which missed ending up behind the person who was hit.
- For the handgun ammo (don't know whether the numbers are the same for the shotgun ammo) the projectiles reach their full spread (14" diameter circle) around 8 - 10 feet from the muzzle. They then travel at that spread for only about 6 more feet, after which they start to collapse inward again. They didn't mention what the effective max range is. The idea here is to minimize the chance for collateral damage on clean misses. They are targeting the 21' and closer typical SD scenario.
- The sections of the projectile are weighted in the tail end. This is how they ensure they spread and fly at the 'proper' angle at the ends of the tether. This results in they sections keyholing on impact. The designer indicated that because of the weighting they weathervane on impact, thereby changing the vector of travel and 'better' transferring the energy to the target.
- On the high cost, what they are saying is that you don't buy these and practice with them regularly... instead you shoot some to ensure your weapon handles them ok, then you just load 2 as the first 2 rounds in your carry magazines. Their rationale is that they developed this whole concept based on statistics that show that most first and second shots in gun fights are misses (75-93% are the numbers they quote). So you use these to improve the odds of connecting on those first 'panicked' shots.
All that said, in terms of penetration, you only have so much energy imparted to the whole projectile when it leaves the muzzle. You are then dividing that energy in three ways [more really due to the hub of the tether] by splitting the projectile in thirds. So for each projectile it is 1/3 the mass carrying 1/3 the kinetic energy. There was discussion in one of the videos about it only having 1/3 the surface area as well, but that's not how it flies or impacts. The weathervaning may reduce the surface area as the portion moves through the flesh, but (by their own admission) causes the vector to be changed.
That sounds to me an awful lot like something that could limit the depth of penetration in favor of doing more damage on shallow tissue. And, I suspect that's why none of the videos I found did tests into ballistic gelatin. For 12 gauge shells you clearly have enough energy to split 3 ways and still have good power. For handgun ammo, especially a 9mm though?