Not true. This is for NFA firearms. Legitimate, select fire m4s, are not legal to own. Due to restrictions put in place by the FOPA revisions of the GCA of 1968, any full auto firearm produced on or after May 19 (EDIT: forgot date) 1986 is NOT legal for civilian citizens to own, tax stamp and BATF registration or not. The first m4s only came out of production and started getting used in service that very year, 1986. Therefor, you're going to have an extremely hard time finding any m4 legally owned by a civilian. This does not include any semi-automatic replica or alternative model. Even if it did, semi-automatic firearms are not regulated under the NFA, unless being converted (which I'm pretty certain is also illegal). That being said, there may or may not be a very small gap between the end of production and the FOPA of 1986, which could have resulted in a very small number of them being owned and hence, grandfathered in under the FOPA regulations. I'm not sure of the exact date, so I can't say for sure. But I can assure you that it is nowhere near as "perfectly legal to own" nor as "easy" as you describe it to be. Just a little background =)
