You can sell guns privately… What you can’t do is go to the store and buy a gun for your buddy or friend.
Now if you go buy it and turnout you don’t like it or want to sell it, it’s legal to do so. But if ATF finds out you went to the store bought a gun did the background check walked out and handed it over to someone else you are in big trouble.
If you so much tell the store it’s for some one else it’s illegal to sell to you. Including if you say it’s a gift for your brother. If that’s the case he needs to come do the background check himself.
My gf has bought me pistols before but she can’t take them home and give them to me, she wrapped the case while the gun store held onto the gun, then I go in do background check and take gun home. It’s the same as long gun.