Do magazine mods affect your gun when it uses heat sinks?
If I have a gun that uses heat sinks/cooldown instead of bullets, does applying a magazine mod to it affect how long I can shoot before it needs to cool down?
Yes it does.
I have a sniper rifle with heat sinks. When I built it I could only fire one shot before it overheated. After developing a skill with +20% ammo capacity it can fire 2 shots before overheating.