Re: Gun show
The biggest problem with the Feral database is the fact it is incomplete as many do not bother to enter the names of those are to be on it regularly. There was a recent shooting in Texas were the shooter was supposed to have been banned from owning a gun but the USAF could not be bothered to fill out the paperwork to put him on the list.
The only time there is no background check is a private sale but I would recommend that one do due diligence on the buyer (like as posted said have a gun shop run a background check). Gun dealers are always required to do at least the Feral check and must refuse the sale if the purchaser fails. States and cities may add more requirements but not less than the feral ones. Again fail the additional requirements; no sale. Also 'straw purchases', sending a person with a clean record to buy a gun for someone who cannot own one, is also a felony (Feral I believe).
If you read the story, his attempts to buy a gun were denied by the background check. What he did was try to circumvent the check by making a gun using a 3-D printer. He was successful in making but he forgot the ban also included possession. Not being familiar with 3-D printers but knowing the parts that get you trouble are the parts that see the most stress during firing I would be concerned that those parts are not to spec. Thus the gun would work for a few firings but might be susceptible to a catastrophic failure.
Biting the hand that feeds IT
