It depends on the route you go to get your tax stamp for the NFA item. If you get your tax stamp with a CLEO sign off then the answer is no. No one else may touch/handle/borrow the item. If you choose to do a trust, then any trustee of the trust may legal use the item. When you get a NFA item and tax stamp with a trust you do not own the weapon, the legal entity, "the trust" owns the weapon. Would be no different than if you worked for a private security firm that had class 3 items. If you were and officer of that company or had documentation stating from an officer of the company that you were allowed to use the item it would be legit. I think this though is rarely enforced as you see plenty of youtube videos of groups of people at the range taking turning with the toys. I would guess that if you got on the wrong side of the law and they wanted to make an example of you they could.