This topic has already been hashed and rehashed here.
The reason for the change in definition who needs an FFL is to have a pseudo universal background check system and to do away with people who buy and sell guns that do not have an FFL.
The guy the ATF murdered in Arkansas was buying and selling without an FFL. Arkansas does not require background checks for private sales. That guy was ordering new guns from an FFL, doing the 4473 to get them in his name then turning around and selling them at gun shows for a profit with no paper sales. I think he got highlighted because numerous guns where he was the original buyer wound up being recovered at crime scenes.
I have already verified numerous times with the ATF that you can sell personally owned firearms without having to get an FFL. The hang up comes if you are buying guns to resell. I have seen that many times at gun shows where a "private sales vendor" will buy a gun then put it right back out for sale on their table. Those are the guys they are focusing on. Some states allow that while others do not, the ATF is trying to back door the states that allow private sales by changing their definition of "engaging in the business".
Now, to be fair, the ATF are, indeed, lying sacks of shit.
The AutoKeyCard debacle and the imprisonment of Matthew Hoover at CRS Firearms. He knew a guy named Kristofer Ervin who made these metal cards about the size of a business card. On them was a etched drawing of an auto-sear called a "lightning link." If you were to cut along the lines, you could put this in your AR and get continous fire. Then, take it out and throw it away. Both Erwin and Hoover talked with the ATF several times about whether or not it was okay to make what is a novelty. It is not a machine gun because you cannot just place the card in the gun and have it work.
Was it okay to even talk about it? Yes, you could talk about it. So, while not actually selling the product, Matt got a sponsorship for talking about it on his YouTube channel.
Then, just about overnight, they ATF decided that it was, in fact, a machine gun. And to receive a sponsorship for just talking about it constituted conspiracy to distribute machine gun parts.
Not to mention the prosecutor, with the help of the ATF, dropped Terabytes of data of discovery at trial.
So, the ATF lies. And if they will lie about that, how easy is for them lie and say, no, don't worry, private party to private party sales are covered by this? Very easy.
So, here is the 3 step process to determining when the ATF is lying:
1. Their lips are moving
2. Sound is coming out in the form of words while the lips are moving
3. It is a day that ends in the letter 'y'
Edited to add:
ATF gunsmith tried to make it work and could not.
So, to amend and be more correct, ATF are incompetent liars.