First is that autos are regulated at the federal level. Everything from fuel economy to impact resistant bumpers. Should a defect be found the product is recalled. Even if the car has been sold multiple times the registration systems at state level can track down the current owner and notify them.
Guns are exempt from Consumer Protection Laws and can only be recalled voluntarily by the manufacturer. The standard for factory recalls on guns is "does it function as designed" and as a result if it shoots a bullet it passes.
If a half dozen people are hurt by a defect in a car it is forced into recall and a repair made to prevent further injury. GM had an ignition switch with extremely light rotational force causing the weight of a heavy key ring to turn the ignition to OFF and thus killing the engine, power steering and breaks. Glock pistols are known for a light trigger pull and short trigger travel. Enough people are injured by Glock handguns to have a name, Glock Leg Syndrome, yet the company has not recalled the product. We really don't know how many people the Glock has injured because the company is allowed to keep that data secret.
Every time a vehicle crash is investigated an improvement is made to the product. Yet guns are essentially the same as they were in the 1880s and the gun lobby fights tooth and nail to prevent any new technology regardless of how reliable. There are currently two smart guns available that have been tested beyond Mil Std and have been shown to be 5 times more reliable than the average production gun yet the NRA and gun lobby has convinced gun owners that they are helplessly unreliable and can probably be disabled by THE GOVERNMENT.
Repeal the PLCAA, place guns under the Consumer Protection Act and give the government authority to place safety standards on them. There are currently 11 mandated safety features in the passenger compartment of cars. There are 0, zip, nada, none placed on the manufacture of guns.
Go figure . . .