If you renounce your citizenship, you forfeit your gun rights. Period. Read the questionare on the federal firearms form 4473 that has to be filled out when purchasing a firearm from a licensed dealer in the U.S. If you renounce your citizenship which is a “yes” answer on the form, you walk with no gun. It’s federal law.
You are right.
Of course, if you are renouncing your citizenship, staying in the USA is pointless.
There are exemptions for "loans" or rental for lawful sporting purposes even by aliens and citizenship renouncer's, you would have to have a valid nonresident hunting license to loan or rent a gun. There are also exemptions for corporations of person who have a corporation in the state they wish to purchase said fire arm if one owned a corporation in a state that does not prohibit foreign owned corporations of person then there is an exemption that such a corporation even if majority owned by a renouncer could still transfer a fire arm. This is the same loop hole that LLC use to get around the chief law officer requirement for class 3 tax stamps, Corporations are individual entities in the code so the former citizen is not in possession nor purchasing the firearm the corporation is and that is perfectly legal. The code is long but its all in there. There is some legal debate about if a corporation allows a person disqualified under part 5 which includes former citizens to posses for more than temporary legal sporting use. The whole thing is mentalmasterbation as if your going to give up your passport why would one remain stateside? Your are right that under the yellow form a former citizen is disqualified but there are many ways around that form I just showed the most common 2.