D.C. POLICE CHIEF Maurice Turner Jr. has decided to increase the department's firepower by issuing 9mm semiautomatic weapons and installing shotguns in patrol cars. That decision is a frightening commentary on the increasing amount of drug-turf violence involving criminals with sophisticated weapons. Some 35 of the city's 46 homicides this year have been drug-related. Already in 1988, about 400 firearms have been confiscated. Most were automatic or semiautomatic weapons.

D.C. police now carry .38-caliber, six-shot revolvers, the same weapons used by most police departments for the past 50 years. They must be reloaded one bullet at a time. Many police officials feel it is time for a change. Chief Turner said that police are "being confronted by a lot more firepower" and that 9mm weapons will "give the police officer parity."

Although most police departments place shotguns in patrol cars, semiautomatics are much less common. But Maryland State Police recently decided to issue them, following 185 arrests on Interstate 95 of drug couriers who were armed with automatics. Prince George's County police are also considering a switch.

Nearby states bear much of the blame for the District's current difficulties. Maryland requires a seven-day wait before a gun purchase is allowed, giving police time to run a background check on the buyer; but Virginia, West Virginia and North Carolina require no waiting period or background check. A bill now pending in Congress would require such a waiting period. It should be passed.

The decision to upgrade police weaponry puts an even greater burden on administrators to make certain officers are carefully trained in the use of semiautomatics. Police must be more concerned than ever for innocent bystanders, and they must give great attention to the terms on which those new weapons are to be used.