In Alia's words.
"The Alter Disrupter Pistol MK4-1, the combined research from the ARC series pistols, and further advances in the Chimera and Gryphon energy unit fields creates a firearm that is nearly a perfection of the ARC series as a whole, however, this comes at a loss as this weapon has no safety measures to assure the user won't be harmed by using it, this makes it only usable by those who could shrug off the damage inflicted once fired, meaning machines are the only ones capable of utilizing this weapon, the contributing factor to this restriction comes in with the newest technology that causes an energy bolt to harden as it leaves the barrel, creating a physical projectile from a cooled energetic slag that is fired, it leaves no trail of residue, this removes all concern for the barrel to be blocked by any obstructions from this process, there in lie the problem, as this process requires far more power to properly utilize, which requires a faster cooling, as the back of the weapon will open to vent out a high temperature vent that could potentially burn the user in the event of an overheat, producing temperatures in excess of 93.3C. Only one was produced, a second one seemingly appears to exist in the labs, it is no more than a shell."