I'd laugh but it would sound like weeping
The game isn't set up to handle the complexity of uses for this type of ammunition but we have code that allows HEAT to be used against helos and yes I can just imagine the howling if I reduced the HEAT pen but, as you say, nothing is really known.
For all the information I have gathered since I started looking into this and other nations "guns" the US tactical doctrine would seem to indicate than APFSDS is the tank killer and HEAT is reserved for lighter targets like APC's and now helicopters as well as 'soft' targets. No commander is going to order HEAT loaded to deal with a tank unless they are low on APFSDS and for nasty people close in they have the M1028 but we cannot simulate that in the game which is why M1028 tanks are segregated as "CS". Also, we cannot simulate accurately the subtle changes made to M830A1 over M830 except that we already allow limited targeting of helos by tanks.
On top of that the actual penetration for M830 seems to be a state secret let alone what M830A1 can actually do and what we had been giving what amounted to M830 ( 60 ) and M830A1 ( 70 ) may or may not be even close but given what's known about other HEAT rounds it seems a logical assumption. However, given the uses HEAT is put to by the US army whether it can penetrate 60 or 70 is really a moot point as it's not used against targets where it might be debateable it would penetrate or not. That's what the APFSDS is for
Now and right now I'm trying to find out of M908 is a general issue round or only issued to engineering tanks. This is a derivative of M830A1 and was first developed to deal with hard concrete objects when the 165mm M123 demolition round was removed from the Army inventory when the M728 was retired According to Globalsecurity it was found that a modification of the M830A1 high explosive multi-purpose cartridge (2-pound High Explosive warhead fielded in 1994) did as well as, if not better than, the 35-pound M123 warhead at reducing obstacles. but, of course. we don't reduce obstacles in the game with high explosive directly so much of what M908 can do isn't relevant to the game unless you are dealing with houses or bunkers and although GlobalSecurity does say "The steel nose allows the projectile to “burrow” itself inside the obstacle before the warhead functions" no mention is made about HOW FAR.
Much of what amounts to OOB work involves digging up info on things governments don't want you to dig up
Furthermore, the M830 is supposed to be the same as DM21A1 and the info I have so far for that that's close is "120mm DM12 HEAT 70cm " ( but I haven't dug to deep into German rounds yet, that's still on my to-do list )
Don