I don't know if you can still do this. But in the past, if you had paperwork not disapproved, when you went to the store to pick up, you could buy a second pistol with no paperwork. As long as you did not step out of the store once you took possession of the first one.
This was pre-one gun a month.
Long gun, yes. You can buy as many as you like on one set of papers/nics call.