Shadowrun: Chummers In Low Places
John Harper wrote:
Light armor is 2 load. Heavy armor is 3 additional load, for 5 total. See page 88.
Armor also affects fictional positioning. If you're wearing heavy armor, then some dude punching you probably has limited or zero effect. To hurt someone in heavy armor you need a plausible attack.
The GM sets the effect level of attacks. If you think that a couple punches should have no effect on heavy armor, then say that.
When a player chooses to expend an armor box, it's used up until they have downtime.