James “Whitey” Bulger bought at least 15 handguns and a 12-gauge shotgun while he was on the run as one of America’s most wanted fugitives, according to firearms tracing reports filed in federal court in Boston.

The reports filed Thursday indicate that Bulger may have shopped at gun shows in Nevada and Utah, buying weapons from private sellers who are not required to conduct background checks or even ask for identification.

In 2000 or 2001, Bulger is believed to have called a Utah man who placed an ad in the “Thrifty Nickel,” or a similar newspaper, selling a 45-caliber Auto Ordnance pistol. The seller, who is not identified in court records, told agents that he sold the gun to the caller — an older man fitting Bulger’s description — outside a mall in Orem, Utah, because “he did not want to have the person come to his home,” according to court documents.

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The reports detail efforts by the Bureau of Alcohol, Tobacco, Firearms and Explosives to trace 29 weapons — pistols, revolvers, shotguns, and rifles — that the FBI found stuffed in the walls and bookshelves of Bulger’s Santa Monica, Calif., apartment after he and his girlfriend, Catherine Greig, were arrested in June 2011 after 16 years on the run.

“Obviously anybody who managed to elude one of the most determined manhunts in US history would certainly figure out a way to buy weapons in Southern California,” said New Bedford Mayor Jon Mitchell, part of a group of mayors pushing for stricter gun control, and also a former federal prosecutor who oversaw efforts to track Bulger. “In the case of private sales, no background check is involved and that’s obviously a large loophole in the system.”

Bulger, 83, a longtime FBI informant, is charged with 19 murders in the 1970s and 1980s as part of a sweeping racketeering case and is slated to stand trial in June in US District Court in Boston. A judge has scheduled a hearing Wednesday on whether he should rule on Bulger’s claim that a former federal prosecutor promised immunity for his crimes, or leave it for the jury to decide at his upcoming trial.

The Brady Handgun Violence Prevention Act, which took effect in 1994, the year before Bulger became a fugitive, requires federally licensed firearms dealers to conduct background checks on prospective buyers, but does not apply to private sellers. Most states do not require private parties — citizens whose primary business is not selling firearms — to conduct background checks, keep records of sales, or ask buyers for proof of identification.

Mitchell conceded that universal background checks probably could not have stopped someone like Bulger, who had fake driver’s licenses from several states, from getting guns. But he added that in the wake of the massacre of schoolchildren in Newtown, Conn., in December, and other mass shootings, more gun restrictions are needed.

“I don’t think anyone should think background checks will solve everything,” Mitchell said. “The aim really is to reduce the risk generally that guns will fall into the wrong hands. Once a weapon is in the stream of commerce it’s very hard to track.”

All of the firearms seized from Bulger’s California apartment had serial numbers, enabling the ATF to trace the weapons from the manufacturer to the licensed dealers, who must record the first purchase date.

But federal law prohibits the ATF from maintaining a computerized database of firearms sales and most states do not require private owners to keep records, making the process of tracking a gun from one buyer to another time consuming and often impossible.

The tracing reports of the guns seized from Bulger, which were first filed in court last June with redactions and then refiled on Thursday with more complete information, reveal that agents were unable to determine when and where Bulger acquired most of the guns.

The weapons were shipped to federal firearms dealers, who sold them between the 1940s and 2006. In most instances, the trail went cold after a licensed dealer sold the gun to a private party.

One of the 45-caliber pistols found in Bulger’s apartment was originally sold by the Sierra Specialty Shop in Wellington, Nev., in April 2004. The shop’s owner, Ginger Sagran, told the Globe during a phone interview that she sold the pistol to a friend, who is a regular customer, and that she never sells a firearm without making sure she knows who is buying it.

“We know that we did not sell it to Whitey, how he got the gun I don’t know,” Sagran said. “Unfortunately, the rules and regulations on gun control only affect honest people. They will not keep the guns out of the hands of criminals because if they want them they’ll get them, even if they have to steal.”

The man who bought the pistol from Sagran told ATF agents that he sold it two weeks later at “an unknown gun show” and “he has no idea who he sold the gun to,” according to the reports.

A 45-caliber Colt pistol, initially sold by a licensed dealer in Henderson, Nev., in 1999, was traced to a buyer, now deceased, whose wife said “he bought and sold guns all the time at gun shows in Nevada and Utah.”

Glenn Pierce, the acting director of the Institute for Security and Public Policy at Northeastern University, said guns can easily be bought in some states from private sellers without any paper trail and universal background checks would slow down the flow of guns to some people who should not have them.

“The highly motivated, highly knowledgeable individual is more likely to beat the system even if it’s a little harder,” Pierce said. “We’re really looking at whether you can stop the less motivated individuals.”