If guns were treated like other consumer products; the manufacturers could be sued when they don't work -- not when they work as intended. (E.g. misfires when needed for self defence, or blows up when fired.)
They are, actually. Nothing in that legislation prevents a product liability lawsuit when the gun has a design flaw that is not addressed. This is how the
Bryco Arms company ended up being sold for scrap in 2003. Quite a story.