Kirk1701mv shows a modification of a GM7.5 M1911A1 model gun, a collaboration between Mule and Tanio Koba. He explains that the primary change involves removing the detonator from the barrel to convert the firearm from a firing model to a dummy cartridge specification. This adjustment allows the user to utilize dummy rounds, which are heavier and provide a more realistic weight and appearance to the model gun while it is on display or being handled manually.