A federal grand jury in Washington is investigating a $13 million arms deal between a South Korean company and Blue Sky Productions Inc., a Northern Virginia firm, and is trying to determine whether Blue Sky had ties to the Old Town Armory, an Alexandria gun shop.

Former investors in the gun shop include Rep. William Dickinson (R-Ala.), the ranking minority member of the House Armed Services Committee. Dickinson said that he was not involved in Blue Sky or in the arms deal for 200,000 M1 rifles and that he sold his interest in the gun shop early last year. He nevertheless has found himself ensnarled in the probe because of his friendship and business relationship with a grand jury witness, according to Dickinson.

The witness, Rene Carlos Vos, died last November in a puzzling private plane crash that also killed his flight instructor. The FBI is investigating the crash, sources said, to determine whether it was a murder-suicide by Vos, an act of sabotage by a third party or merely an accident.

Sources said Vos had been testifying under immunity before the grand jury investigating the arms transaction, which Vos did not initiate but helped arrange. Vos had been an investor in both Blue Sky and the Armory. He helped arrange the deal through Blue Sky, but sold his interest in July 1986, a month before the arms contract was signed.

According to federal and other sources, the grand jury's investigation includes three questions:Did any members of Congress or lobbyists have both a role in 1984 legislation that made the arms deal possible and a personal financial stake in the transaction? The improper use of influence by U.S. officeholders could violate various federal laws. Were improper payments made on behalf of U.S. arms dealers to Korean officials in an effort to arrange the deal? Payments made to influence officials abroad could violate the Foreign Corrupt Practices Act. Is there any business or legal relationship between the two Northern Virginia firms, Blue Sky Productions Inc. and the Old Town Armory? If there is, investors in either firm could be the subjects of investigations into transactions by the other firm.

The Old Town Armory specializes in the sale of "quality firearms" -- including machine guns -- locally and for export, according to the business cards of store employees. A notice on the wall explains the procedure for Virginia residents to buy a machine gun legally; another notice invites foreigners to ask for details on how they may buy guns.

Dickinson, Vos and two other men set up the Armory in 1984. Dickinson is well known to his colleagues on Capitol Hill because he wields considerable power and influence when it comes to the nation's defenses.

Vos helped negotiate the arms deal through Blue Sky, another Northern Virginia firm in which he was part owner, but in which Dickinson had no interest.

In several interviews, Dickinson said that neither he nor the gun shop was involved with Vos or Blue Sky in the arms purchase. "This whole thing is nonsense to me," Dickinson said. "I wish I had never heard of that store."

As far as the arms deal was concerned, Dickinson said, "I didn't know much about it. I was his {Vos'} partner in another business, but I sold my interest in that a year ago. I'm telling you the absolute truth."

Under the weapons purchase contract, the M1s were to be obtained for between $51 and $76 each and for a total of $13 million. An M1 rifle in good condition retails in the United States for $300 or more. A conservative gross income on the sale of the rifles would be $60 million.

The M1 Garand rifle, a semiautomatic weapon that fires .30-caliber bullets from an eight-round clip, was the standard infantry weapon in World War II and Korea. It is much admired by collectors. No civilian version was ever manufactured.

The tale has all the twists and turns of a mystery novel. It involves the two Northern Virginia firms, which had two common investors but apparently no other ties, a former member of Congress convicted in the Abscam prosecutions, lobbyists for the National Rifle Association and a former deputy assistant secretary of defense.Saga Begins in '84

The story starts in 1984, when Congress approved an amendment to the Gun Control Act of 1968. The amendment apparently made the arms deal possible, and a contract was signed in 1986. However, Treasury Department officials blocked the transaction in September of that year after rifle shipments had started. Lobbying and legal maneuvering ensued, and Congress acted again, in the continuing budget resolution signed by President Reagan last Dec. 22, to free the deal.

Dickinson said he "had nothing to do with" the 1984 amendment to the Gun Control Act. The amendment was considered by both the House Ways and Means Committee and the House Energy and Commerce Committee. Dickinson serves on neither.

Dickinson also said he did not discuss with other legislators the provision in last month's continuing resolution to allow the deal.

Dickinson said he heard last spring that the FBI was looking into his ties with Vos, although he said he had not been interviewed by the FBI. He said he learned of the FBI's interest from Anthony Speros Makris, who joined with Vos and Dickinson to found the Old Town Armory in 1984.

Dickinson said Makris told him that the grand jury had questioned Vos about a letter Vos had written to an unidentified third party stating that Blue Sky and the gun shop were associated.

Bank records from Blue Sky, the Old Town Armory and some individuals including Dickinson have been obtained to help the grand jury, the sources said.

Makris is a former roommate of Vos' and a self-described close friend of Dickinson, who was with Dickinson so often, Makris said, that other representatives incorrectly thought he was on Dickinson's staff. In August Makris resigned as the deputy assistant secretary of defense for House affairs, a job in which he worked directly with Congress, representing Department of Defense interests. He had held the post since March 1985.

Makris declined to comment about the investigation or about his conversations with Dickinson.

The FBI and the U.S. attorney's office have declined to comment on the investigation into the arms deal, which began late in 1986, or the probe into the Nov. 19 plane crash.

Among the questions asked Vos before the grand jury, sources said, were several about former representative John M. Murphy, a New York Democrat and Korean war hero who was convicted of conspiracy, conflict of interest and accepting a gratuity in the Abscam prosecutions in 1980 and defeated for reelection the same year.

The grand jury has been looking into Murphy's role in arranging the arms deal, sources said.

Murphy acknowledged through Myles Ambrose, attorney for Blue Sky, that he had been questioned by the FBI in the presence of an assistant U.S. attorney last June. He said he had never been questioned before the grand jury.

In May 1984, Vos, Dickinson, Makris and others founded the Virginia Firearms Corp., the official name of the Old Town Armory, according to the Virginia State Corporation Commission (SCC).

In an interview, Dickinson described himself as a friend of Vos, whom he said he had met several years ago when Vos was a gun dealer in Montgomery, Ala. Dickinson said he invested in the Alexandria gun shop because he had known Vos from Alabama and occasionally went hunting with him. In December 1984 Richard (Preacher) Whitner, a military sales consultant, bought an interest in the store, according to Whitner.

In 1985, Vos and Wayne LaPierre incorporated Blue Sky Productions in Alexandria. LaPierre is the director of the National Rifle Association's Institute for Legislative Action, and Vos sometimes acted as a lobbyist and consultant for the NRA, according to LaPierre.

Virginia SCC records and federal firearms license applications do not show any relationship between the Old Town Armory and Blue Sky. The Armory's Alexandria address, 215 King St., and telephone number appear on Blue Sky's application for a federal firearms license that was filed in October 1985. Since then, Blue Sky has used addresses in the District, New York and, most recently, Arlington. $13 Million Transaction

In the summer of 1986, Blue Sky arranged the arms transaction in a contract with the Daewoo Corp. of South Korea. Under the contract, Blue Sky was to pay $13 million for 200,000 U.S.-manufactured M1 rifles of 1950s vintage and import them to the United States for resale.

Congress' 1984 amendment to the Gun Control Act permitted for the first time the importing of military weapons that had been reclassified as "curios or relics." The amendment came after heavy lobbying by the NRA and other groups and appeared to make legal the importation of such World War II-era weapons as M1 rifles, many of which are in storage or in the hands of forces in other countries.

When the first shipments of 40,000 M1s arrived in San Francisco and Seattle in September 1986, U.S. Customs officials questioned accompanying documentation showing that the weapons had originally been purchased from the United States by South Korea. Under Treasury regulations, if the weapons had been acquired by the Koreans as part of a U.S. military assistance program, they could not have been imported legally. Customs stopped the shipment and suspended the import permit, according to court documents in a lawsuit Blue Sky has filed against the government to regain the import permit for the arms deal.

With the weapons impounded and the transaction imperiled, Blue Sky received support from powerful allies in an effort to resolve the problem. Exhibits in the lawsuit include letters in support of the shipment coming from Edward J. Derwinski, counselor for the State Department and a former House member from Illinois, and Lt. Gen. Philip Gast, then director of the Defense Security Assistance Agency, both of whom argued that Korea needed the income from the weapons sale to reequip its armed forces.

Last January, a few weeks after Derwinski and Gast wrote the Treasury Department, Customs freed the shipment of 40,000 weapons because that transaction had been completed, but refused to allow the remaining 160,000 rifles into the United States. Treasury officials cited another law, the Arms Export Control Act of 1976, which prohibits the importation of any U.S.-made military weapons bought by another country under a U.S. sales program, apparently conflicting with the Gun Control Act amendment.

Shortly thereafter, 20 House members -- including such influential representatives as Jamie L. Whitten (D-Miss.), Edward P. Boland (D-Mass.) and G.V. (Sonny) Montgomery (D-Miss.) -- signed the letter to Treasury Secretary James A. Baker III urging him to overrule the decision by the Customs Service and the Bureau of Alcohol, Tobacco and Firearms blocking completion of the deal. The letter was written on the letterhead of Rep. Bill Chappell (D-Fla.), chairman of the defense subcommittee of the House Appropriations Committee.

Dickinson did not sign the letter.

Congress got back into the act last fall, and by the time the legislators completed the continuing resolution on Dec. 21, it contained a provision amending the Arms Export Control Act and, in effect, reinstating Blue Sky's revoked import permit.

The legislation contains an unusual provision giving the government 20 days to quash the deal, if the administration declares the legislation contrary to policy or if the attorney general objects on the grounds that the measure would interfere with a criminal investigation.

Chappell said in an interview that the provision was adopted to make the Arms Export Control Act consistent with the congressional intent of the 1984 Gun Control Act amendment. He said that House-Senate conferees drafted the 20-day kickout provision because they were aware of the criminal investigation and did not want to jeopardize it. No Federal Action

No federal actions concerning the transaction had been taken by yesterday, according to spokesmen for the agencies. The deadline runs out next week.

The ownership of both the Old Town Armory and Blue Sky has changed since the firms were founded.

Dickinson's 1987 financial disclosure statement shows an interest in the gun shop worth between $15,001 and $50,000, as well a debt owed to him by the gun shop of between $5,001 and $15,000.

Last April 6, the Virginia Firearms Corp. (the legal name of the Old Town Armory) filed its annual report with the Virginia SCC and listed Dickinson as a vice president.

Dickinson said his 1988 disclosure statements will show that he sold his interest in the Armory in early 1987. He said he did so in part because the shop occasionally sold handguns and other weapons to diplomats, and he wanted to avoid the appearance of selling arms as a private businessman to foreign governments.

Makris said he recently sold his interest in the gun shop.

Robb Roudabush, the current manager of the Old Town Armory, said he recently acquired a two-thirds interest in the business and that there is no connection between the shop and Blue Sky. Roudabush, who said he has been associated with the shop for 18 months, said Vos told him he, Vos, had been given immunity to testify before the grand jury.

The NRA's LaPierre, in an interview, confirmed that he formed Blue Sky with Vos and said the company was organized to promote rock concerts. He said he "severed ties" with the firm in the spring of 1986, before it became involved in the arms business. He said that although he could have invested in an arms deal legally, to do so might have created the appearance of a conflict of interest because of his position with the NRA, and he said he told Vos he would not be involved in the deal.

Federal records show that LaPierre was listed as Blue Sky's secretary-treasurer on an application for a firearms import and dealers license that was filed four days after the company was incorporated in Virginia. That application was signed only by Vos. LaPierre said he was unaware at the time that Vos had made such an application.

LaPierre, in his role as an NRA lobbyist, said he actively sought the Gun Control Act amendment in 1984. He also said his lobbying was not related to his forming Blue Sky the following year.

Vos and LaPierre formally transferred their interest in Blue Sky in 1986 to Whitner and Robert Frulla, an Annandale businessman, Frulla and Whitner said in an interview.

Ambrose, the attorney for Blue Sky, said Frulla and Whitner were not involved in the passage of the 1984 law. Said Ambrose, "We were merely trying to take advantage of it and make a few dollars."

Ambrose said that FBI agents have interviewed Frulla and Whitner and that both men have had long meetings with a federal prosecutor. Frulla and Whitner were told they were not subjects of the investigation, Ambrose said.

Ambrose said it was evident from those meetings that the FBI and the U.S. attorney's ofice are looking into whether an "interrelationship" exists between Blue Sky and the Old Town Armory.

According to Ambrose, the arms deal started in 1984 as the brainchild of Dong H. Choi, a Korean-born California businessman, who then enlisted Murphy, the former New York representative. Ambrose said neither Choi nor Murphy (who was released from prison in 1985) was involved in the 1984 legislation that appeared to make the gun deal possible.

According to Ambrose, Murphy contacted Frulla, a friend of 25 years, and Frulla brought in Whitner.

Frulla and Whitner said Vos was included in the arms deal in 1986 because Vos told them that Blue Sky had already received the necessary federal firearms license and import permit and because Vos was familiar with marketing firearms.

Frulla and Whitner said they were unaware that the NRA's LaPierre was also an owner of Blue Sky.

Vos and Choi traveled to Korea in June 1986 to inspect a sample of the weapons and to negotiate a preliminary agreement with officials of the Daewoo Corp. When Vos returned, Ambrose said, Frulla and Whitner became alarmed because they thought that Vos was trying to set up a side deal with a competing company.

After threatening a lawsuit, Frulla and Whitner agreed to pay Vos' expenses to Korea -- which they said were more than $11,000 -- plus various corporate legal fees in exchange for ownership of Blue Sky, according to court documents.

From that point, Frulla and Whitner said, they had no further contacts with Vos concerning the arms deal. Whitner continued as an owner of the Armory with Vos and others.

Frulla and Whitner replaced Vos at Blue Sky with James W. Stone, an arms expert and former vice president of Interarms Inc. of Alexandria, and Smith & Wesson Co., which has an office in Arlington. Choi also became an owner of Blue Sky.

Choi could not be reached for comment.

The new Blue Sky owners completed the negotiations Vos had started with Daewoo and signed a contract in August 1986 to import the 200,000 rifles.

Stone, Frulla and Whitner said they do not know why the FBI has continued to investigate the deal, but they said they have been told by Assistant U.S. Attorney Robert R. Chapman that they are not subjects of the probe. Through long discussions with Chapman and FBI agents, Ambrose said, it was clear that Vos was a subject of the investigation.

Chapman declined to comment.