Okay, we all agree that the individual, not the tool, is responsible for his or her actions, correct? If Joe Somebody went out and shot someone, we should judge his actions based on, among other things, his intent. We should not hold the gun responsible in any way, as it is an inanimate object.
We also all agree that it doesn't matter what the designer's original intent was, a tool can be used for whatever it's owner wishes. Again, the individual's willful decision to use the tool to whatever purpose is what matters, not the tool's original design intent.
So why, then, are we arguing whether or not guns were designed to kill? Anti's, of course, want to bait you into some slippery slope where if you admit "Guns were designed to kill," then "Guns should all be banned." But this does not follow. If it does, then I don't see it. Someone please explain to me how I can conclude "Guns should be banned" from "Guns were designed to kill." The most important factor, personal accountability, is completely removed.
When we say "Guns were designed to kill," we're describing it from an engineering standpoint. No more, no less. When an Anti says "Guns were designed to kill," they're hoping to attach a moral (or immoral, rather) value to guns so they can judge (and therefore control) an inanimate object. As pointed out earlier, the end result of banning inanimate objects goes counter to their original goal. Again, that's because they want to avoid blaming the individual by blaming the tool. Faulty reasoning. Won't work.
So why are we debating whether or not guns were designed to kill?