The House Assasinations Committee formally jettisoned its $6.5 million "bare bones" budget yesterday and decided to try to struggle along for the rest of the year at less than half the price.

Anticipating House approval for continuing their investigations into the murders of President Kennedy and the Rev. Martin Luther King Jr., after a dubious winter, committee members also voted a new resolution to keep them in business for the remainder of the 95th Congress - until 1979.

Del. Walter E. Fauntrey (D-D.C.) said he thought the proposed new budget of $2,796,650 for calendar 1977 would be "certainly platable" to the House. It includes approximately $250,000 already spent this year while the committee struggled for survival in the face of a series of disputes.

Committee chief counsel Richard A. Sprague endorsed the new allotment reluctantly. He warned that the cutback make it impossible to complete the investigations within the expected two years.

Sprague had contended that his original $6.5 million budget couldn't be cut at all without compromising the inquiry, and he made plain yesterday that he had no intention of eating those words.

Instead, he said he was relying on the assurances of his two, top deputies, Robert Yanenbaum and Robert Lehner, who told him they felt they could conduct effective investigations with the slimmer budget.

"I have gone along with their recommendation," Sprague said. "It is less than I would propose, but I am willing to go ahead."

Rep. Richard Preyer (D-N.C.), chairman of a special budget task force for the committee said, the biggest savings was realised by cutting the proposed staff from 70 to 115 persons, meaning a $2,334,100 reduction in projected salaries.

The new proposal would provide a 27-member task force, under Tanenbaum's direction to investigate the Kennedy assassination, and 27 more, headed by Lehner, to investigate King's murder.

The inquiry would still be the most expensive investigation ever undertaken by Congress, but House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass) professed his "wholehearted support" for it this week after a private briefing from the ranking Democrats on the committee.

It was also plain, from the figures presented yesterday, that next year's budget for the committee, with a full-strength stuff of 115, will be about $1 million higher.

The House Rules Committee is expected to take up the resolution reconstituting the committee early next week. The budget will be submitted later first to the House Administration Committee and then to the house floor.

The Assassinations Committee spent the rest of the day in secret session for a briefing on the progress of the Kennedy and King investigations. Chairman Louis Stokes (D-Ohio) told reporters that it included a rundown on the committee staff's prison interview Tuesday of James Earl Ray, who is serving a 98-year term in Tennessee for King's murder.

"He was very cooperative," Stokes said of Ray. The chairman, however, indicated that the interview was primarily a got-acquainted session, and said, "It may be necessary to talk to him many times" before considering any public testimony.