JUST to set things straight with the airgun silencers, it does not matter whether or not it can be detached. As long as the sliencer cannot be attached to or used on an actual gun (caliber differences, threading), it is legal to have one for airguns. I have an airgun that shoots 1500 fps (breaks sound barrier, 22 crack), and I have tried the pop bottle method and it works nice for backyard plinkin.