I need to extend my rifle and I wanted to make a mold of the end 5 inches of it. I figured it would hold the piping better and look more authentic. So if anyone has done this, could you let me know what your choice for the negative and how you'd go about it? I've got some 407 latex casting rubber, but I don't want to mess up the rifle by putting it directly onto it because I've already sanded off the crappy finish that was on it to stain it black later.