Police officers who fire their revolvers without adequate justification are rarely subjected to stiff disciplinary penalties by their departments, a new study of police firearms practices in Washington and six other cities has found.

"Department disci line in shooting cases seems lenient if not perfunctory in many cities," says the research report, published by the Police Foundation, a private nonprofit group. "Apparent violations of both the letter and the spirit of department policies have been condoned either by outright justification or by extremely mild discipline."

Despite this "pattern of leniency," the study said, there is an increasing trend toward stricter curbs on the use of firearms by police officers. "The trend in most large cities stems to be toward limiting the use of deadly force to situations involving self-defense, the defense of others, and the apprehension of suspects in violent or potentially deadly felonies," the study said.

In other findings, the 193-page study reported most victims of police gunfire are black. In 30 shooting incidents during 1973 and 1974 in the seven cities, the report found, 79 per cent of the civillians killed or wounded by police gunfire were black.

While the percentage of blacks shot by police is "disproportionately high" as compared with the percentage of blacks in the seven cities' populations, the report said, "the figure corresponds quite closely to black arrest rates" for serious crimes in the same cities.

The study found that 57 per cent of the civillians shot by police were armed with guns, knives or other weapons. It said that a "sizable percentage" of the incidents involved officers who were not in uniform. Seventeen per cent were off-duty officers and 18 per cent were plainclothes police.

The other cities on which the findings were based included Birmingham, Ala., Detroit; Indianapolis; Kansas City, Mo., Oakland, Calif., and Portland, Ore The authors of the report are Catherine H. Milton, former assistant director of the Police Foundation; Jeanne Wahl Halleck criminal justice consultant here and wife of D.C. Superior Court Judge Charles W. Halleck; James Lardner, a freelance writer and former D.C. police officer, and Gary L. Abrecht, a D.C. police lieutenant.

In examining how police departments deal with incidents in which their officers fire their weapons, the study found that almost 92 per cent of the shootings either were ruled "justified" or failed to result in punitive action against a police officer In Washington, the report said, the figure was slightly lower - 84 per cent.