Erm, sorry to tell you, but there are.
Nevertheless, both weapons (one for secondary and one for primary) have the very same ratings, including same AP and sabot PEN and range.
Which is quite annoying I grant you.
But behold, what ammo do you pout into your coax 20mm? If you have BOTH AP and APDS handy; and can fit only one? Maybe that's why there are similar capacities for both.
No, wait, the AP vs Sabot rating changes in the AMX10P with the time.
So I guess it was meant to improve something.
Maybe APCR rounds are hard-coded to give better results but I doubt it, since it can also represent weaker AP round.
To put it shortly, dunno
