Unlike the original game which had a Heavy Ammo chest that the entire team had to gather around to be handed its contents, in destiny 2 the person who picks up the Power Ammo first will get the goodies.
In each of the different game types found in the Crucible there will be Power Ammo that are located on both sides of the team and one at a neutral location. Getting control of the neutral power ammo is an important factor in these games as it doesn't respawn thus provides the team who collects it with an instant advantage. The non-neutral Power Ammo that can be found on either side of the team respawn every 90 seconds from when you took it.