The 4th U.S. Circuit Court of Appeals upheld yesterday the firearms and attempted property damage convictions of Jewish Defense League activist William R. Perl, but overturned his conviction on a conspiracy charge.

Perl was found guilty of illegal receipt of a rifle and attempt to damage property used by foreign officials in connection with a 1976 attempt to shoot out the apartment windows of two Russian officials living in Prince George's County.

Perl helped carry out the shooting as a protest of Russian treatment of Soviet Jews. No damage was done because the man who fired the weapon, Reuven Lev-tov, a former member of the Israeli foreign service who is now a U.S. citizen, used blank cartridges supplied by the FBI.

Lev-tov, described by the Circuit Court opinion as "a shadowy and intriguing figure," testified at Perl's trial that he had decided to induce a Jewish leader into an act of violence and then turn him over to authorism in an effort to combat terrorism carried out in the name of Jewish causes.

Perl appealed his conviction on grounds that U.S. District Court Judge Edward S. Northrop should have permitted the jury to consider an entrapment defense. The three-judge Circuit Court panel said Northrop was correct in ruling out entrapment because the government was not involved in inducing Perl to commit a crime.

The conspiracy conviction was overturned by a 2-to-1 vote of the panel because, the majority said, Northrop failed to correct fully an erroneous instruction telling the jury it could consider Perl's dealings with Lev-tov as well as alleged unnamed coconspirators. Lev-tov was not named in the conspiracy indictment.