The most detailed exceptions in these house rules concern modeling firearms and other weapons with an eye towards increasing their realism- both in the real world and dramatic sense.
While the changes are focused on the weapons themselves, others rule modifications were need to improve the representation including Hit Locations/damage application, BODY, bleeding, Killing Attacks, and even Combat Skill Levels.
A few important new limits were also required- Barrier Defense and Armor Effect.
Attention to one area without consideration of others would result in a failed attempt at improvement and one is advised to consider all the house rules on this site with an eye towards how they impact the goal of a more representative and dramatic weapon simulation.
None of these changes produce a truly realistic outcome. Real Life is not so easily modeled that it can fit nicely within a game system, let alone one designed originally for superheroic comic book action like HERO. What it will do is nudge events in the game to more closely resemble some expected real world outcomes.