I've always wondered about this.
Scenario: Let's say someone with an NFA item dies and leaves their entire estate to their children. Now, let's say the children are unable to have the transfer done due being younger than 21. However say that this person would hate to forfeit the NFA item. Is it possible to have this on hold in the keeping of a trust, etc. ?
I wish I had family members as into firearms as me (not that I'm suggesting I want something bad to happen to my family, quite the contrary), but more so I am curious as to how picky the ATF is with issues along these lines.