So I believe the Forerunner weapons in Halo 4(Light Rifle,Scattershot,Binary Rifle, Boltshot,Incinerator Cannon) shot out bits of hard light. Am I mistaken here?
If they shot hard light what exactly is the ammunition you have to reload? Why do you even need to reload? The Forerunners were SO technologically advanced compared to the UNSC or Covenant why would they have weapons you need to reload? Hell even a lot Covenant weapons don’t need to be reloaded and instead have a battery, if Covie tech was engineered from Forerunner tech then shouldn’t the Forerunner weapons have batteries too?
Possible canonical reason: the weapons used by Promethean constructs/Composed Prometheans operate without the benefit of a high-grade combat skin. As such, they are not powered by the suit’s external reactor and require individual recharge spheres periodically.
It seems to me that when wielded by a Promethean Knight the weapons are recharged like batterys by the Combat Suits they seem to be wearing that S282 refers to somewhat. The weapons however also seem to be designed in a way that they can be easily picked up by humans and anyone else fit to wield a weapon. However with no source of power to recharge the weapons internal battery or cool it the hard light ammunition within is forcibly ejected and the user is forced to reload the weapon as well. It would seem to me the weapons were designed specifically to function with Promethean Knights and other possible constructs similiar to them, however they were also crafted in a way that a organic being could also use the weapons, specifically Forerunners, Humans, it would appear.
In all honesty this makes the Forerunner weapons much more capable, and efficient than the Covenant weapons. They dont overheat and they arent limited by a battery that cant be recharged during battles, this makes the weapons very similiar to Humanitys while also hinting at the connection between the Forerunners and Humanity. The Covenant Carbine also seems to be engineered from similiar technology, as it is also a rifle that shoots both a ballistic, energy, ammunition. So I dont think it has much to do with gameplay at all, it in fact makes the Forerunner weapons that much more dangerous in my opinion both Canon wise, and Gameplay wise.