i agree with what you're saying, in-so-far as the 'typical result' of a gun is not killing; many (if not most) guns haven't been involved in killing anything. however, i think even if a gun is never used to kill, it can still have killing as a 'primary function,' much in the way a seat belt's primary function is to keep you alive in a car accident, not be vaguely uncomfortable.
The seat belt's primary function is to control the rate of your deceleration - period. Keeping you alive is a side-effect of doing so. In fact, the function of a seat belt goes beyond just what happens on impact, but also extends to keeping you in position to control the vehicle even before/without collision.
I see your point, but I'd counter with considering the measured lethality of a gun is generally/rarely, if ever, a primary design constraint with handguns. If it were, there are a great number of guns that would have never been made/sold in smaller calibers and shorter barrels which impede both their accuracy and lethality.
To put it bluntly, there are a number of guns that are designed primarily to be a bluff when you consider their actual effectiveness in a violent encounter. Too few rounds, too much recoil for their size, short sight radius, feeding reliability, small/ineffective caliber for the purposes of penetration, etc...
In the case of rifles where this has been a factor, lethality (of humans) is not the primary concern so much as creating the largest most devastating wound for the purpose of taking the subject "out of the fight". In the case of game animals - there you have the best case of rifles being design specifically to kill as effectively as possible.
Then there is the matter that if guns' only purpose is to kill, then why do police officers need them? Are they killers?
What about the security details for politicians and celebrities? Are they killers too?
It's sort of like saying nuclear weapons only exist to blow up cities. There you have the best match of design constraint, function and intent. However, in practice their primary function was political leverage...