In fact, children under 15 are about 40 times more likely to die by swimming pool than by an accidental firearms discharge [0].
I still have a pool. There are reasonable laws about having auto-closing gates and a fenced-in yard. I don't see anyone clambering to tighten restrictions on assault swimming pools.
Likewise, semi-automatic, detachable-magazine-fed rifles are responsible for something like 2% of shootings. The only real place they have significance is in mass shootings. The only refute I have to, "but if we ban these rifles we won't have shootings" is that it would just happen through a different means. The Happy Land Fire killed 87 people, not a shot fired. Timothy McVeigh killed 189 people with fertilizer... and that was in 1995 -- under the "Assault Weapons Ban" of 1994.
[0] http://www.m1-garand-rifle.com/gun-safety/firearms-versus-sw...