So I was watching a video about field stripping the rifle, and one of the first steps mention was to loosen the flash suppressor to relieve tension on a spring all the way back in the receiver? Im not really knowledgeable about m4's/ar-15's etc... but is that normal? Or something specific to this rifle? Is there some kind of a spring or something running all the way down the length of the barrel between the suppressor and the receiver? Thanks!