The age limit for buying a handgun from an FFL doesn't prevent young reckless individuals from obtaining handguns. You can pretty easily buy a handgun used from someone which is perfectly legal at 18 years old. But here's the kicker. If you inherited a handgun as an 18 year old, if you take it to an ffl to get it cleaned or repaired, you risk never getting your firearm back. The way the law is worded, is that an ffl is prohibited from transferring a handgun to anyone under the age of 21. Including handguns being transferred for reasons other than selling it.