What properties should my fictional HEAT rounds have to punch through heavy armor and ERA?

Question

I have some forcefield shielding in my setting whereby particles act essentially as solid mass armor for all intents and purposes. Warheads grind themselves down against armor just like modern composite armor. As a result, most tanks in my setting use the shield as the main armor, with a backup layer of ERA (explosive reactive armor) and slightly thicker structural metal underneath it. However, these shields are much tougher. They can routinely shrug off multiple long rod penetrators. They also have the added benefit of detonating HEAT (high explosive anti tank) as soon as the round hits the edge of the forcefield since it acts as solid armor.

Somethings to note about HEAT:

1. It utilizes the Munroe effect to fire a superplastic round (usually a copper lining) to punch through a tanks armor.
2. It does NOT rely on temperature to melt armor.
3. Standoff distances matter, detonate to early and you cannot get a good enough jet.
4. As a superplastic jet travels, it breaks apart and stretches. Usually within two meters.
5. The velocity of the HEAT round has absolutely zero bearing on penetration. The velocity of the molten jet is usually hypersonic (fictional material can go higher if that helps the answer).

The large shielding capabilities of my force field means that I can get multiple meters of equivalent armor in a very compact particle field. Combined with active protection systems (on top of ERA) and there very quickly comes up a problem. Tanks can essentially push a region unimpeded unless facing equivalent armor.

I'm looking to give my infantry and lighter armed vehicles a fighting chance. In this case instead of copper, I am using a fictional material that retains its superplastic shape without breaking or stretching too much. Especially past the two-meter mark.

What properties does this fictional material have such that my new HEAT rounds can penetrate through my particle shield and through my ERA blocks?

Note it doesn't have to be surefire/guaranteed all the time to penetrate all the way through. Basically, I'm looking for a materials upgrade so that things become more even. An answer can approach from the assumption that the material already exists and make assumptions/observations about said material to achieve the goal.

By properties I mean characteristics such as density, thermal/specific heat indexes, elasticity, crystalline structure, behavior under heat etc etc. The answer doesn't have to answer all the above points but is just a frame for the type of answer I'm looking for, essentially the materials engineering.

Answer 1

Anti-Shielding Rounds

The enemy tanks have energy shielding. What kind of ammo is good against that? Why anti-shielding rounds of course! There are two flavours:

1. Diamagnetic Rounds The jet is made of a special metal that reflects the shield backwards across a thin layer on the outside. The outside of the jet is stopped by the shield but the inside punches straight through.

2. Anti-Harmonic Rounds Before firing, the charge is set to vibrate with the opposite frequency of the energy shield harmonics. This lets the projectile ignore the shield.

Diamagnetic rounds are more expensive. They are made of rare metal. But they work on any shields. Anti-harmonic rounds are less expensive. But you need to know the shield frequency before you fire.

Of course the above is word salad. But energy shields are word salad in the first place. So it's all good.

Answer 2

Terror drone.

https://www.deviantart.com/lizzuzci/art/Terror-Drone-272009744

This is lifted from the Red Alert franchise. These are little spider bots. They scramble onto vehicles and get inside.

Terror drones are very cheap, costing only 500 per unit or, if an Industrial Plant is built, a mere 375. They can be used to attack ore miners, the only downside being that they would exit a chrono miner when the latter chronoshifted back to the ore refinery.

Due to the terror drone's extremely fast speed, it is very difficult to catch them before they reach their targets, but their lack of armour makes them easy to destroy.

Your tank armor is all designed to prevent fast moving explosives. The terror drones scramble along quickly but none of the hypervelocity stuff. They scramble up onto the vehicle and start scraping. The particle fields work better against fast moving impactors because the velocity of the impactor induces a proportional response from the charged particles. Explosive armor is moved aside by the drone. The scraping is a bad noise to hear from inside the tank.

Once the thing is on the tank and digging it needs to be dislodged by accompanying infantry or someone inside the tank who comes out and shoots it. If the tank sees one of these coming it can shoot it.
A lot of times no-one sees it coming - they position themselves and dig in, and then spring out to attack a passing vehicle.

Those using terror drones know that these will be addressed personally by opposing troops. Most are decorated with marker-drawn messages for the opposing troops. Messages and pictures purported to be of relatives of opposing troops.

Answer 3

Stacked rounds

Two rounds fired at once. The second is in flight a couple of meters behind the first. The first round is a small HE round or perhaps DIME (Dense Inert Metal Explosive) designed to dissipate the shield enough to allow the HEAT penetrate to the ERA.

Once the ERA has been hit a few time later rounds will penetrate the actual armor.

Combined with UV dye to allow subsequent shots to hit the already damaged location.

Answer 4

Fuzzy slippers

The shield is composed of particles. What keeps those particles in position as the tank moves? What determines their position in the first place?

The particles move along the outer membrane of an EM field generated by an antenna on the tank.

Shield particles are strong against physical impact, but if an object that approaches the field has a powerful electrical charge, it can attract or repel the particles without contacting them.

Shield-penetrating rounds have a special metal casing that can hold a charge. The gun barrel has rifling but also some harsh fuzz, like a shag carpet of metal. When the round is fired, it acquires a strong static-electric charge from friction inside the barrel. When the round reaches the target, its charge repels the particles in the shield field, allowing the core of the round to pass through an empty region of the target shield and reach the target.

The good news is that the charge setup can theoretically be retrofit onto guns of just about any size (although handgun bullets are already so small that there's not much "core" to hit the shielded target with).

The bad news is that the barrel fuzz wears out pretty quickly, so the charge of successive shots diminishes. The fuzz treatment significantly reduces muzzle velocity, meaning you get less range. And the interaction between the incoming round and the shield is complex and random, meaning that the portion of the round that pierces the shield has a random deviation, and will impact the target in an unpredictable spot in a cone projecting from the point of shield entry. (An enemy can increase their shield radius in hopes of yielding a cone that might result in clean misses, although there is no guarantee.)