Senior officials at the Justice and Treasury departments have privately expressed strong reservations about legislation -- officially backed by the Reagan administration -- that would weaken the 1968 Gun Control Act, according to administration sources and documents.

The documents say that Attorney General Edwin Meese III told a conservative group that he has serious reservations about parts of the bill and that these concerns were repeated by Justice Department officials in a January meeting with lobbyists for the National Rifle Association.

The Treasury Department's Bureau of Alcohol, Tobacco and Firearms (BATF) detailed 13 objections in an internal memo last week, saying that the bill would make it harder to prosecute gun-wielding criminals.

The split within the administration is over the McClure-Volkmer bill, which is backed by the NRA but opposed by most law enforcement groups.

The internal divisions became clear yesterday at a hearing of the House Judiciary subcommittee on crime, where Chairman William J. Hughes (D-N.J.) released some of the documents.

Deputy Assistant Treasury Secretary Edward T. Stevenson denied any change in position, saying that "Justice, Treasury and the White House are still consistent in support of" the bill. Stevenson said the measure strikes "a balance between the rights of law-abiding gun owners on the one hand and the requirements of law enforcement on the other."

Under questioning from Hughes, however, Stephen E. Higgins, director of Treasury's firearms bureau, acknowledged that his agency objects to key provisions.

At the Justice Department, spokesman Patrick Korten said: "We fully support the bill, and Ed Meese wants to see it passed. No amendments are needed. Whatever concerns we and Ed Meese may have, we believe they can be fully resolved through a colloquy on the House floor to establish a legislative history."

Meese declined to send a representative to the hearing, saying that he would defer to the Treasury Department. An administration official said this was meant to signal that the Justice Department finds "several things wrong with the bill." Hughes said yesterday he thinks that the attorney general "has very serious reservations" about some provisions.

The bill, sponsored by Sen. James A. McClure (R-Idaho) and Rep. Harold L. Volkmer (D-Mo.), proposes the first major change in gun control laws in 17 years. It passed the Senate 79 to 15 in July, and 170 House members have signed a discharge petition to bypass the Judiciary Committee and move the bill to the House floor. A majority of 218 is needed.

In a Feb. 10 memo, Higgins listed six positive aspects of the bill and 13 criticisms, such as its ban on surprise inspections of gun dealers. "The prohibition against unannounced inspections would enable unscrupulous licensees to conceal violations of the law," he wrote.

He also criticized its weakening of mandatory penalties for using a gun in a violent crime. "The bill may be interpreted to allow a fleeing felon to avoid the penalties where he used a firearm to make his escape," he wrote.

Higgins also took issue with the easing of record-keeping rules for dealers and owners, saying that this "would hamper law enforcement's ability to trace firearms." And he said a provision to legalize the interstate transportation of unloaded, inaccessible firearms "would impede the efforts of state and local law enforcement officials" to enforce the law.

Another BATF memo said that Meese told the conservative 721 Group "that he had problems with the bill; that the bill was no longer necessary since the administration had solved the problems that gave rise to the bill . . . and that he was particularly concerned about the provision of the bill on mandatory penalties."

NRA spokesman John Aquilino said BATF's concerns are "nonsense" and "sound like a serious disinformation campaign." He said the issues were dealt with in the Senate bill and that "there's no wavering by the administration as far as we're concerned."

Higgins conceded at the hearing that he receives few complaints about record-keeping, a target of the bill, and that each year only 4 percent of the nation's 225,000 gun dealers are inspected. "We cannot break publicly with the administration," a BATF official said later. "But we went in there and told the truth."