After vigorous lobbying by the National Rifle Association, the Senate Judiciary Committee yesterday approved legislation that would make it easier for Americans to obtain both rifles and handguns. But gun-control advocates led by Sen. Edward M. Kennedy (D-Mass.) were able to win some major concessions.

The legislation, introduced in the Senate by Sen. James A. McClure (R-Idaho) and in the House by Rep. Harold L. Volkmer (D-Mo.), would be a major revision of the 1968 Gun Control Act.

Its most important effect would be to lift most prohibitions against the sale of guns across state lines and to make it possible to obtain mail-order guns, provided that the buyer has met the seller face to face at some point.

But Kennedy, with the support of Judiciary Committee Chairman Strom Thurmond (R-S.C.), was able to win an amendment requiring handgun purchasers to wait 14 days to pick up their weapons to give local police departments time to check them for criminal records.

Such a waiting period was endorsed by the Attorney General's Task Force on Violent Crime, but was opposed by the NRA. Donald Fraher of Handgun Control Inc. called the vote "the first positive step for handgun control since 1972."

Kennedy also won an amendment providing a mandatory jail term of at least two years to anyone convicted of a crime in which a firearm was involved.

That change also went through with Thurmond's blessing.

"This is the way to get at this problem, I tell you. People need guns in their homes to protect themselves," he said, adding that there should be severe punishments for people who use guns to threaten others or to commit a crime.

The McClure-Volkmer bill would provide these major changes in the nation's gun laws:

It would loosen the definition of a gun dealer to provide that persons who make occasional gun sales do not have to register or keep records. Critics say that convenience stores or pawnshops, such as the one that sold the gun John Hinckley allegedly used to attack President Reagan, could sell guns without registering as dealers. An amendment by Kennedy to prohibit gun sales by pawnshops was defeated.

* It would allow private citizens to import foreign firearms.

* Dealers would be allowed to sell firearms from their "personal collections" without keeping records. Critics say unscrupulous dealers would be able to evade the record-keeping requirement by shifting handguns from business inventories to their personal collections.

* It would restrict government inspections of dealers' records and require prior notice. Proponents claim that the federal Bureau of Alcohol, Tobacco and Firearms has harassed innocent dealers.

Kennedy offered an amendment, requested by some police departments, to ban the sale of armor-piercing bullets. "There is not a deer in Massachusetts which wears a bullet-proof vest," he said, adding that the bullets serve no legal purpose.

But the amendment was set aside for discussion later, when the bill reaches the Senate floor, probably not until summer or fall. Sen. Robert J. Dole (R-Kan.) said he is interested in a similar amendment that might also affect sales of Devastator bullets like the ones allegedly used by Hinckley.

The McClure-Volkmer bill was approved on a 13-to-3 vote, with Kennedy, Sen. Charles McC. Mathias Jr. (R-Md.) and Sen. Howard M. Metzenbaum (D-Ohio) voting against it.