WASHINGTON (AP) _ Proponents of a bill backed by the National Rifle Association won two crucial test votes in the House on Wednesday when they crushed moves by gun control advocates to maintain federal controls on handguns.

The victories suggested the NRA has the votes it needs to win passage of a bill to ease many restrictions of the 1968 Gun Control Act, passed after the assassinations of Martin Luther King Jr. and Robert F. Kennedy.

After the two votes, the House adjourned until Thursday morning, when debate will resume on two competing firearms bills.

The gun lobby's measure is sponsored by Rep. Harold L. Volkmer, D-Mo. A measure backed by police and handgun control organizations was offered by Rep. William J. Hughes, D-N.J.

Hughes created the test votes when he tried to saddle the gun lobby's bill with key provisions of his own legislation - including maintaining the current law's ban on interstate handgun sales and maintaining state and local controls over transportation of handguns across state lines.

Hughes lost his first major test 248-176, on an amendment package that included the interstate sales ban and the interstate transportation provision.

He then tried the transporation language in a separate amendment that lost 242-177.

The Volkmer bill would allow both interstate transportation of handguns and interstate sales.

Hughes had argued that his amendment would ''remove the label of cop killer legislation'' from the NRA's bill.

''The issue boils down to who we're going to support: the police or the NRA and their self-serving interest,'' Hughes said.

Rep. John D. Dingell, D-Mich., a member of the NRA national board, said the Volkmer bill ''does not make it easier for criminals to get guns'' but protects ''law-abiding'' citizens from burdensome regulations.

Rep. William M. Hendon, R-N.C., asked the House to uphold the Volkmer bill ''for the good old boys in rural America who deserve reform of the Gun Control Act of 1968.''

Rep. James A. Traficant Jr., D-Ohio, a former sheriff, said the Hughes language would ''give a psychological edge back to our police officers.''

The Hughes amendment would have ended the current ban on interstate purchases for rifles and shotguns and guaranteed the right of transportation for those guns across state lines. But this wasn't enough to sway the majority of House members.

The Hughes amendment also would have kept stiff record-keeping requirements for gun dealers, prohibited future possession of silencers and retained current dealer licensing requirements.

Hughes' own bill would continue the ban on interstate sale of handguns, leave rules on interstate transportation of handguns to state and local governments, order a police records check afterd a handgun sale is made and ban future possession of silencers.

The Volkmer measure would allow interstate sale of all weapons, and guarantee their transportation across state lines. It ha no records check provision or ban on silencers, would ease record-keeping requirements for gun dealers and make it more difficult to prosecute anyone who unintentionally violates gun laws.

Both would expand federal law that requires add-on automatic prison terms for use of firearms during commission of certain crimes.

Rep. Peter W. Rodino Jr., D-N.J., chairman of the House Judiciary Committee, said as debate opened that it was more important to protect police officers and citizens from handgun killings than to ''accommodate sportsmen and hunters.''

Volkmer said the time for changing the 1968 act has ''been a long time in coming.'' He said his bill would ''return constitutional rights to the citizens of this country. Civil rights do apply to gun owners as well as to all other Americans.''

Hughes forces said the gun lobby's bill would enable more criminals to obtain handguns. The NRA and allied groups contended the Hughes bill would imposes too many burdensome controls on law-abiding citizens without hindering criminals.

Hubert Williams, president of the Police Foundation, acknowledged that police groups ''were quite surprised by margin'' by which the Hughes amendments were defeated. But he added: ''We're not lawmakers or professional lobbyists. We're police officers.''

Sarah Brady, wife of presidential press secretary James Brady and a board member of Handgun Control Inc., said, ''I thought it would be a little closer.'' She expressed hope that the House would overturn its initial decision on interstate handgun sales.