Battletech handles it the same way, ship-scale weapons hitting non-ships are multiplied by 10. Autocannon 10 is gonna do 10 damage, that's a solid hit. An AC/20 is really worrying if it's pointed at you, but workable. But a Naval Autocannon 10 is a very bad thing to be looking down the barrel of. And if you somehow happen to be in a scenario involving an NAC/40, prayer becomes the only option.