IT'S true, a ban on the sale of assault weapons and large-capacity cartridge clips wouldn't prevent all killings like those that took place in Killeen, Texas, last week. But such a ban would undoubtedly curtail the wide availability of the rapid-fire weapons favored by mass killers. It would erect one very practical barrier in front of disturbed individuals bent on murder.The House of Representatives, all too predictably, didn't see it that way. The day after the Killeen massacre a substantial majority of congressmen stuck to their guns, so to speak, and struck from the anticrime bill a provision that would have banned many semiautomatic guns as well as multibullet magazines like the one used in Killeen. The logic that prevailed, as it has so often in the past, is that criminals kill, not guns. Pro-gun forces revel in suggesting that baseball bats, scissors, cars, and other implements that people may use to kill one another should be banned too. It's really no different with a handgun that can pump out 17 rounds in a couple of seconds, they argue. When was the last time someone with a pair of scissors killed 23 people and wounded dozens of others in the space of a few minutes? Then there's the "you ban assault weapons and next it'll be my hunting rifle" argument. Why does one follow the other? Nobody is calling for the elimination of all firearms. Gun lobbyists respond to tragedies like Killeen's with expressions of sympathy for the victims and calls for stronger law enforcement - both sincere emotions. One National Rifle Association spokesman observed that these mass killings wouldn't happen if people like the Killeen murderer were put behind bars where they belong. Is he suggesting we push aside such legal niceties as due process of law and round up everyone who displays hateful or unbalanced behavior? Better to begin with such rational steps as waiting periods, background checks - and a ban on the sale and ownership of weapons that have no legitimate recreational or protective purpose. A few lawmakers, like Rep. Chet Edwards, whose Texas district includes Killeen, rejected the gun lobby's logic for the first time and voted for the ban - despite the probable political backlash and despite the White House's opposition to the measure. Perhaps next time the issue reaches the floor of Congress - as it surely will - more legislators will turn from the old illogic.