A Pentagon investigation into the Grenada gun-smuggling case has focused on Navy Cmdr. W.J. Roble, a member of Vice Adm. Joseph Metcalf's staff who was ordered to obtain the captured weapons brought back by Metcalf in 1983, Roble's lawyer said yesterday.

Meanwhile, a congressional source familiar with the investigation said Metcalf is expected to be cleared of wrongdoing in the case, with blame for bringing the Soviet-made rifles back from Grenada shifting to Roble.

Metcalf, who commanded the U.S. invasion of Grenada in October 1983, has admitted "sole responsibility" for returning with 24 AK47 automatic rifles despite federal and military prohibitions. The Pentagon's inspector general reopened the case after news reports that Metcalf got off with no more than an administrative warning while several lower-ranking servicemen were ordered jailed for up to three years for smuggling and, in some cases, selling the weapons.

ABC reported last night on its "20/20" program that Metcalf will be found "essentially blameless" by Pentagon investigators but that Roble will be "accused of serious charges regarding the guns."

Michael Fasanaro Jr., a Norfolk lawyer retained by Roble, said investigators have twice sought to question his client and sent a "threatening" letter warning that their findings would be turned over to the Navy for "possible disciplinary or administrative action."

Roble has refused to be interviewed by investigators but submitted a written statement two weeks ago outlining his role in the case, Fasanaro said. Roble, then a lieutenant commander on Metcalf's staff, says Metcalf told him to pick captured weapons from a military warehouse for the admiral to give as souvenirs after the Grenada operation, Fasanaro said.

Metcalf told an Army colonel to take Roble to the arms cache, where he obtained the AK47s and marked several with staff members' initials in hope of reserving rifles for them, the lawyer said.

Customs officials, waiting in Norfolk for the aircraft on which Metcalf and his staff returned from Grenada, seized the weapons. Although servicemen are allowed to bring home "war trophies," automatic weapons are prohibited.

Metcalf has told probers that he ordered Roble to obtain captured weapons for souvenirs but was unaware they were automatic, a congressional source said.