So in the state I currently reside, I can buy a firearm from a friend with cash. There is no bill of sale, no record at all tying me to that firearm.
While this is ideal for maintaining my own privacy from our government, it applies to everybody, including those people down the street that fly a thin blue line flag in their yard.
I'm really conflicted on how I feel about it, but it's pretty clear which gun owners have a propensity for unreasonable violence.
Case in point: https://en.m.wikipedia.org/wiki/Shooting_of_Ralph_Yarl
We live in the world we live in. Get armed and get your friends armed. Train.