Perhaps I don't have enough coffee on board but I cannot seem to find it. Would someone be so kind as to point me to any type of ATF decision/ruling/edict that says machines guns can have whatever barrel length I choose. I just want something I can print and add to my range binder. As it would turn out my coworkers all like to shoot at an old National Guard range that damn near abuts the current police range. Ducks in a row and all that.

Thanks.
MIke

It works the other way. You cannot find anything regulating the length of a machine gun barrel.

Call the local police ahead of time and tell them you will be shooting NFA as a courtesy. I call the local sheriff before I go, never had anyone even care, stop etc. I did get a thank you from them once for telling them.

That is what I gathered digging through the ATF website and the CFR's. It is not a SBR nor is it "also" an SBR. Why? Because it is a machine gun.

Clearly spelled out would have been handy.

Thanks

You're not going to find it.  It's just a given.  Machineguns are exempt.