AP warhead on missiles

[PlasmaKrab]

Hello all!

First a physics question: has anyone here any hard evidence to claim EFP (explosively-formed penetrators) warheads as being closer from HEAT penetrators that AP warheads?
In terms of temperature, velocity...
I know it stands broadly on a middle ground between the two (HEAT and sabot).

The question is about the various EFP weapons (cluster bombs or ATGMs) vulnerability to ERA.

In the same way, I was wondering why the KEM/LOSAT was modelled with a HEAT warhead in the game (obat12 USA, weapon 162), while, to simplify it awfully, a KEM is a rocket-assisted sabot round?

I have tested it with an AP warhead, the results seem equivalent, total penetration against level-1 ERA, some rejection from advanced ERA, but few.

So shouldn't the various KEMs be modelled with AP warheads instead?

[scJazz]

Straight forward physics would indicate that EFP/SEFOP/SFF rounds resemble AP rounds in terms of similar effects. An armor piercing round generally is thin, long, and heavy (DU Sabot being the extreme case). Often the round is jacketed. Damage is caused by the release of kinetic energy with the straight forward Energy = Mass x Velocity (Squared???).

An EFP round is designed to overcome the issues with its light weight by having a really insane velocity as compared to a normal AP round. EFP rounds have an effective "muzzle velocity" of 6000 to 8000 meters per second. A quick Google is giving values of around 1500 m/s as the muzzle velocity on an M1A2 120mm smoothbore. In addition since an EFP rounds "muzzle velocity" occurs within meters of the target it doesn't suffer from reduced armor penetration at greater ranges.

Given all of this EFP rounds are similar to HEAT in that their effectiveness does not decrease at range.

They are similar to AP in that damage is caused by kinetic energy and hence is uneffected by ERA.

[Backis]

Errr...

Exactly what energy do you think HEAT deliver? Magic? The difference between an APFSDS and a HEAT jet is where the energy is created (gun barrel as opposed to from the round itself) and how the penetrator is composed (solid preformed as opposed to liquid jet formed by the warhead detonating), not what kind of energy it delivers into the target.


As far as I've gathered the EFP's designed for AT work differs from a HEAT jet in it creating a bigger chubbier slug travelling slower. By being slower it also cools down and harden in flight.

Faster EFP's have been designed for other uses though.

This all makes it harder to disrupt with ERA (the bigger solid mass is harder to disperse than a smaller, thinner stream of liquid metal), and its slower velocity lessens friction during penetration, making composite armour matrices designed to take advantage of that increased sensitivity against friction lack their increased efficiency against EFP.

Another effect from having the larger penetrator "slug" is that it doesn't loose focus as fast, and therefore can be set off at a greater distance from the target. Spaced armour may also become less effective than against HEAT.

[PlasmaKrab]

Thanks for the info!

Obviously the slug's velocity and mass are somewhat inbetween AP and HEAT, depending on the size and principle.

Are there any reports of EFP slugs being used IRL?
The ERA penetration data would help.

[PlasmaKrab]

Regarding the KEMs, I have done some tests and the AP penetration doesn't seem to fall off with the distance like it does with the tank rounds (tested on ranges from 400 to 4750m, pen=200 all the way).

On the first results, the rejection rate of the advanced ERA seems quite low though: 3 times on 16 hits, with 9 ERA tiles on each side.
Does the weapon penetration have an influence on this? Value was the same as for the original KEM (LOSAT), i.e. 200.

[JaM]

It is really interesting, so TOW-2B with AP warhead will be more accurate, as it is top-attack weapon.
About Adv.ERA, try compare rejection rate of tank AP rounds

[PlasmaKrab]

I really have no clue about the various EFP types.
Only ERA vulnerability seems to change, and I have no data on this IRL.

KEM seems obvious OTOH and works perfectly.