IF EVER A U.S. senator wanted to support a strong anti-crime measure and respond directly to pleas from police chiefs across the country, today's the day. S.49 is going to the floor. Unless amended, this bill would gut the current minimal controls on the acquisition of handguns. But with amendments aimed at stopping quick sales, the legislation could be converted into an important anti-crime measure.

No, this isn't another round in the old debate over "gun control." This is a matter of public safety. What the police are seeking in these amendments is in the interest of sportsmen, collectors and anybody else who understands the difference between legitimate purchases of firearms -- for recreation, law enforcement and private security -- and quickie sales of "snubbies" and other concealable handguns to criminals and "impulse" purchasers.

The 14,000-member International Association of Chiefs of Police, the National Organization of Black Law Enforcement Executives, the Fraternal Order of Police, the National Troopers Coalition and the Police Executive Research Forum are calling for two amendments:

*To retain a current prohibition on interstate sales of handguns. Allowing these sales, as the unamended proposal would do, would circumvent existing state and local regulation of handgun traffic and "impair the ability of state and local law enforcement agencies to prevent handguns from being acquired, carried or possessed illegally."

*To add a 14-day waiting period for purchases of handguns, in order to facilitate basic records checks. A waiting period was recommended also by the 1981 Attorney General's Task Force on Violent Crime, since "drug addicts, felons, mental defectives and the like are not the best risk for the 'honor system'. . . ."

Several improvements already have been accepted by original sponsors of the bill. One would remove a sloppy proposal that would have barred prosecution of a dealer for violations claimed to have resulted from "simple carelessness." A second change takes out language that would have preempted state and local license-to-carry laws. Another would close a terrible loophole in existing law that allows the importation of parts to make "Saturday Night Specials" -- the handgun that criminals, not sportsmen, love to tote.

What more does any senator need to hear before joining to turn a bad bill into an important move against violent crime?