Key members of the House Appropriations Committee have tried unsuccessfully to halt Pentagon research and development of a neutron 155-millimeter shell.

They lost, according to aides, because of a Catch 22 situation - they could not make public their arguments against the need for the neutron 155-mm shell because even the fact that the U.S. wants to build one is shielded by the highest security classification given nuclear weapons information.

Unlike Senate opponents of the entire new generation of neutron weapons, these House members supported production of the neutron warhead for the 56-mile-range Lance missile and the neutron projectile for 22-mile-8-inch artillery.

Their objections are lodged solely against the additional Pentagon request for a costly neutron 155-mm shell for an 18-mile-range howitzer.

Although the 155-mm shell three feet long, is less than two inches narrower than the 8-inch artillery projectile, compressing a fusion weapon to the size of a 155-mm shell would represent an extraordinary technical achievement in nuclear weapon-building.

The members who oppose the 155-mm proposal question why it is being done.

The present nuclear 155-mm shell has a yeild under a kiloton. In a 1973 congressional hearing, Maj. Gen. Frank A. Camm, then handling military applications for the Atomic Energy Commission, said the current 155-mm nuclear shell "is able to handle the enemy with far less damage to the civilian populace in which we are fighting than with larger yield weapons . . . You burst them in the air. The blast and radiation damage [is on] the target you are hitting. Then, you can move right through that area immediately because they are airbursts."

The need to limit collateral damage from present high-yield nuclear weapons has been the prime argument for shifting to lower-yield neutron war-heads.

That argument does not hold for the 155-mm program.

According to an informed source, the neutron version of the 155-mm shell would have a substantially higher yield than the currently deployed shell.

The killing range of the neutron radiation it released would be far greater than the deadly range of blast and thermal effects from the present shell.

A National Security Council arms impact statement sent to Congress last year confirms that. It says the neutron 155-mm shell "will produce about a 100 per cent increase in military effectiveness against armored formations."

In short, the neutron radiation from the new shell would kill or incapacitate more enemy personnel carriers than would be destroyed by the blast from weapons in current inventory.

Opponents of the neutron 155-mm argue that with the neutron 8-inch projectile, nothing more is needed. "The program represents the government-owned nuclear weapons laboratories trying to build a tiny H-bomb just to show they can do it," one critic said.

Congressional opponents argue privately that the cost is too much. The price is classified but said to be above $435,000 per shell.

There are more 155-mm howitzers spread throughout the NATO forces in Europe than there are 8-inch tubes. At a House Appropriations subcommittee hearing this year, one government witness said "there are 2,196 dual-capable 8-inch howitzers in Allied Command Europe."

Neutron 155-mm shells would be deployed at Army division level, creating enormous security problems for the new shells, according to some critics.

House opponents of the neutron 155-mm shell got the House to go along with deletion of research funds, primarily because their innocuous language went unnoticed buried in the $10.3 billion public works money bill.

Rep. Tom Downey (D-N.Y.), a member of the Armed Services Committee, said yesterday he was not aware of the deletion although he keeps close tabs on military programs.

But when the bill went to conference with the Senate, John Stennis (D-Miss.), chairman of the Senate Armed Services Committee and of the conferees, said he wanted the House language dropped.

Rep. Tom Bevill (D-Ala.), chairman of the House conferees, said yesterday it was an open meeting and he could not discuss the 155-mm program, so he let it go.

Now Bevill and others won't even say which of their colleagues is against the neutron 155-mm shell, "because it's too classified to discuss."