MS-HEAT

Gun Stats assumes that both shaped charges are the same size!

So you calculate them from the published penetration in millimeters, which comes out as half as much as a single stage, then double that damage.

A normal HEAT round that punches 900mm will do 6dx12(10) cr ex linked 6dx5 cr ex.

An MS-HEAT round that punches 900mm will do 6dx6(10) cr ex linked 6dx5 cr ex, but shaped charge damage is doubled.

If it hits reactive armor, the first charge is consumed and the reactive armor is expended and the second charge does 6dx6(10) cr ex.  If it hits normal armor, then it, effectively, does the same 6dx12(10) cr ex of a normal HEAT round.

Silly me, I've been finding out the penetration of the precursor charge and main charge then adding them.

For example, the PG-29V fired from the RPG-29 will penetrate 900mm RHA, but only 750mm it it's protected by reactive armor.

So that means the precursor charge penetrates 150mm on its own.

I've been showing this as 6dx2(10) cr ex follow-up 6dx10(10) cr ex linked 6dx5 cr ex.

It comes out the same on RHA, but penetrates better when there's ERA than the rules as written.