In a hurriedly-arranged "photo opportunity for the press, the House Assassinations Committee yesterday took custody of 10 boxes of documents and evidence in the murder of Martin Luther King Jr., including the rifle that is supposed to have killed him.

Shelby County (Memphis) court officials turned it all over, item by item, as the cameras yesterday afternoon in the Rayurn Office Building.

Del Walter E. Fauntro (D-D.C.). chairman of the subcommittee investigating the nine-year-old King assassination, gingerly took the Remington and 30-06 Gamester rifle out of its origial black bardboad as case and insected at length.

A latent fingerpring from the rifle was one of the key print has that first led the FBI to identify James Earl Ray is serving a 99-year prison term in Tennessee although he has been claiming in recent years that he was just "a fall guy" in some thus far unexplained conspiracy.

The showing, scheduled after Shelby County Criminal Court officials flew into town with the just-subopenaed evidence yesterday morning took more than two hours. It included everything from three cigarette butts found in Ray's white Mustang to a bloody handerchief and skirt King was wearing when he was killed April 4, 1968.

Asked by a reporter why the "exercise" was conducted. Committee Chairman Louis Stokes (D-Ohio) took exception to the question.

"It's not an exercise," he insisted to reporters. "This is some of the most important evidence in the history of this nation. The committee has the function (of taking custody), not the staff.

The hearing, however, was apparent effort to win support for continuing the committee's investigation beyond March31 when its present charter runs out.

The House instituted the inquiry last September, but the committee has been bogged down almost constantly in disputes over its budget, its investigating techniques and its personnel, culminating in the resonant resignation last week of Chairman Henry B. Gonzalez (D-Tex.).

Appointed Tuesday, Stokes said the committee was still undecided on the King assassination, as some members have suggested, before the March 21 deadline. But at yesterday's hearing, he did put into the record correspondence from Ray indicating that he might be willing to appear before the committee one day and waiving any attorney-client privilege standing in the way of testimony by Percy Foreman, who once represented him.

Stokes and other committee members met earlier in the day with Attorney General Griffin B. Bell to re-establish the committee's access to FBI files. It had been cut off last months as part of Gonzalez's unsuccessful attempts to fire the committee's chief counsel, Richard A. Sprague.