When the House, after six years of debate, finally took up legislation to ban armor-piercing bullets two weeks ago, Rep. Mario Biaggi (D-N.Y.) put the issue bluntly.

"Either you are for cops or crooks," he said.

Not everyone would agree with Biaggi, a former policeman wounded twice in the line of duty. But the House voted 400 to 21 to ban the manufacture, import and sale of so-called "cop-killer" bullets.

The Justice Department, which had opposed the original bill written by Biaggi and Rep. William J. Hughes (D-N.J.), now supports the modified version. It has been endorsed by most law-enforcement groups. Even the National Rifle Association, which helped shoot down the bill last year, agreed to go along.

But a dispute in the Senate killed any chance for final approval before Congress adjourned for the year.

The Biaggi-Hughes measure goes after certain hard-metal bullets that can pierce bulletproof vests worn by police officers. It exempts bullets intended primarily for sporting purposes. Opponents complained that some gun dealers might sell armor-piercing bullets without knowing it, so the bill was changed to cover only "willful" violations.

A similar measure, sponsored by Sen. Strom Thurmond (R-S.C.), would ban only future sales of armor-piercing bullets. House sponsors said this would leave untouched millions of rounds of ammunition now on the shelves, but a Thurmond spokesman said it would be "an administrative nightmare" to round up all the incorrectly marked bullets in stock.

Thurmond tried to obtain unanimous consent for a Senate vote on the measure, but Sen. Steve Symms (R-Idaho) objected. "He sees it as the camel's nose under the gun-control tent," a spokesman said.

Symms offered to go along if his own bill, known as "the Morton Grove amendment," were voted on, too. The bill, named after an Illinois town that enacted a tough gun control law, would bar federal aid to communities that adopt such policies. Negotiations broke down in the rush toward adjournment.

PICKING UP THE TAB . . . The Justice Department is paying the legal fees for five former department officials and a White House aide who were the subjects of a House Judiciary Committee investigation.

The tab, which at one time covered six other administration officials, has come to $60,524 so far.

The committee's 2 1/2-year probe charged that several administration officials lied or acted improperly in withholding Environmental Protection Agency documents from Congress in 1982 and 1983. The panel urged Attorney General Edwin Meese III to seek appointment of an independent counsel.

Officials say the government is paying the ex-officials' bills because the allegations involve their official actions and Justice lawyers were barred from the House interviews. Meese has some expertise in the matter; last spring a court awarded him $472,190 in legal fees for a 1984 independent counsel's probe related to his nomination as attorney general.

Washington lawyer Jacob Stein, the independent counsel in the Meese case, is the attorney hired by former deputy attorney general Carol Dinkins in the EPA affair.