Armistice said:
For proof debunking this common myth see Mythbusters
Warlord Ralts said:
By knockback, I mean: Target gets hit, the kinetic energy knocks them backwards or down.
I saw the episode in question. What the Mythbusters debunked was the ridiculous, Hollywood-esque, three-meters-backwards-through-the-bar-window knockback. If you watch the episode again, you'll see that there
was some knockback from each shot; the targets at least recoiled from the shots, and from some of the closer ranges / higher calibers, the target was actually knocked off the stand. This is what Ralts means by knockback; not the Hollywood misrepresentation, but the actual physical transfer of momentum from one (ballistic) object to another.
Seeing as Ralts has done his fair share of shooting and has been shot himself, I think I'll take his word on matters like this.
As for the ballistics / energy weapon issue: I definitely think that advanced in energy technology would not halt the use or development of ballistic weapons. This is, of course, assuming the setting in question is based on realistic science fiction (if it is more space fantasy, like Star Wars, then it can handwaive anything it wants). I recently read David Drake's
Redliners (a novel I'd recommend for anyone who likes their sci-fi hard & gritty). The book presents both ballistic weapons and energy weapons on roughly equal footing; both have their merits and disadvantages. Personally, I think the main ballistic weapons in the book (stingers) are the scariest handheld weapon I've ever heard described in a novel.
And that's just it. As technology levels increase, ballistic weaponry gets SCARY. The ability to fire smaller masses with greater force and higher speeds makes for some dangerous firepower.