Agree that the old cannon cannot be compared to the A10 warthog gun.
Old cannons came in different sizes and should be compared against each other.
Modern Autocannons should be compared against each other.
As for BT ACs, I stick by what was presented for years going back to when BT started. BT ACs always fired multiple shots similar to
modern Autocannons, they are rapid fire like a machine gun but larger calibers based on era. I remember all the fiction writers, whenever they wrote about an AC 'shot' being fired, it was multiple rounds doing the damage, it did not matter if it was an AC2 or an AC20, they all fired multiple rounds that together did the damage and explained why damage was done to different areas for the bigger ones AC/10 and AC/20.
Strangely, current BT changed to all damage in one place that is an inaccurate representation of ACs (they seem to have done the same for Energy, I read the current BT Quick Start rules and it says LL does all damage to one spot).
MWO seems to have taken some weird hybrid where LL does splash damage that is like old BT while PPC and Balistics do all damage to one spot like new. Peersonally, I believe the last should change, ACs should do splash damage like lasers, not decided on PPC yet.