I have an old Bushmaster Ultralight with a pinned stock that was purchased during the Clinton years. I want to replace the pinned stock with an adjustable stock since these are no longer banned (at least in WV). Never having worked on ARs I am confused with what I have read concerning the difference between a commercial buffer tube and a milspec buffer tube. Which would the Bushmaster require or would it be possible to use either a commercial or a milspec buffer tube? One would think this would be an easy question to Google - but apparently it is not. Back when I bought the gun it was claimed that Bushmaster made a milspec gun so can I assume their buffer tube was milspec?