The concept of the Purifier weapons in was originally inspired by the Dominator Concept from Psycho Pass. However it quickly became altered to become a hybrid of the Dominator Concept, the Judge Dread Lawgiver and the magical stamp hammer of Lavi (D.Gray-man).
These combination ideas gave way to an idea of a magic-tech weapon with select fire capabilities via the use of changing magical stamps. These stamps being on the hammer of the weapon and controlled by an electronic singal. A change in signal causes a change in shape on the stamp. However the idea that the hammer itself would be enough implies that is must carry a great deal of power within it. Which would be impractical for the weapon size. This led to the idea of the putifiers using a special ammunition made from demon forged transmutation metal that when hit with the specific shaped magic stamp take on particular properties.
The concept allows for a variety of weapons including pistols, shotguns, assault rifles and long range rifles.