stancrist said:

What you have described sounds like basically a much more complex and costly version of the Aeroshell projectile.

That looks like a more refined version of the Dagny Dagger.  (Or rather, the Dagny Dagger looks like a less refined version of this, as the Aeroshell appears to have been around longer, at least conceptually.)  The idea seems to work, at least in 9x19mm.  The DD uses what appears to be a NiCu penetrator, but that's only to get around US ammunition laws; as one of its creators said, there's no practical reason why someone couldn't use a different penetrator material.

I'd expect some Hague Convention related gripes from certain parties, especially if Elbonia optimized the sabot for destructive effect on soft targets - an easy thing to do, and one that wouldn't affect hard target penetration.

Mustrakrakis said:

I'd expect some Hague Convention related gripes from certain parties, especially if Elbonia optimized the sabot for destructive effect on soft targets - an easy thing to do, and one that wouldn't affect hard target penetration.

Not sure why? Not a hollow point and would it be more injuring than a regular FMJ?

Forget the polymer layer; tungsten rod will shrug off the aluminum shell shortly after penetration begins due to acoustic mismatch between the materials. A more serious problem is stabilizing the projectile even at PDW velocities and spin rates. I won''t make the calculations for you, but it won't be aerodynamically stable beyond a few dozen meters; lousy gyroscopic moment.

graylion said:

Not sure why? Not a hollow point and would it be more injuring than a regular FMJ?

I'm talking about a non-discarding plastic sabot that essentially explodes in soft targets by design, as in the Dagny Dagger.  It is certainly more injuring than a regular FMJ against unarmored flesh.

Hollow points are not specifically addressed as a problem with the Hague Convention, although that is a common (but not universal) interpretation.  In the case of something like the Dagny Dagger, the complaints would be regarding "...bullets which expand or flatten easily in the human body..." and "...with a hard envelope which does not entirely cover the the core...".  It's simple for JAG and I to dismiss Sierra MatchKings as legal due to violating the letter of the Convention without violating the intent of it, just as it's simple for Europeans to do the same with their open-base bullets, but in a case like this, it's arguably violating the wording and is definitely violating the intent.

I'd expect complaints, but I'm not sure whether or not they'd ultimately matter.  When's the last time a country got in actual trouble for using questionable bullets?

Mustrakrakis said:

I'm talking about a non-discarding plastic sabot that essentially explodes in soft targets by design, as in the Dagny Dagger.  It is certainly more injuring than a regular FMJ against unarmored flesh.

Yes, but that is not what the bullet we are talking about looks like - and not what I'd want. 

ZailC said:

Forget the polymer layer; tungsten rod will shrug off the aluminum shell shortly after penetration begins due to acoustic mismatch between the materials. A more serious problem is stabilizing the projectile even at PDW velocities and spin rates. I won''t make the calculations for you, but it won't be aerodynamically stable beyond a few dozen meters; lousy gyroscopic moment.

Well, we are designing the gun, so we can decide on the spin rate. And how does this work for the Dagny Dagger?

With enough velocity you don't even need a super hard  rod.

300Norma Mag  and 155grain match bullet at 3800fps , punching through 10mm Hardox Extreme like its nobody business. Result was not intentional but a stupid , miscalculation that soft bullet won't damage the plate 

*Hardox® Extreme  nominal hardness of 60 HRC (Rockwell) and typical hardness of 650-700 HBW

That shouldn't be unexpected at all.

This said, punching high hardness steel of wearable thickness isn't terribly difficult compared to punching level 3 ceramics and etc much less esapi grade plates.

Due to high hardness steel its just an abrupt transition from bullet not making any damage at all at sub  3000 fps MV even with .338 to a clean punch through at these kinds of speeds. We kinda always considered 10mm hardox targets safe from most practical calibers with soft jacketed rounds at any distance past 100m , this was shot at cca 150m and a very unusual load and bullet combo for a 300NM 

Similar to M193 zipping through steel that'll stop steel core M855.  Of course, UHMWPE has the opposite problem, will stop the M193 but M855 goes through like butter.