The problem with M830A1 is that it is not a conventional HEAT round.
As it can be clearly seen it is a subcaliber discarding sabot design. Since warhead diameter is one of the most important factor affecting a HEAT warhead clearly this was not designed to maximize HEAT penetration.
The estimates for the older M830 I have seen are indeed all in the 600-700mm of RHA range.
Do you need some loadouts for abrams tanks?