NORTH ADAMS — Over the span of about three weeks, Raul Martinez gathered about 15,000 spent .40 caliber bullet casings.

An artist from Spain, Martinez strung the casings together, put them through a loom and wove a "rug" — a thing of beauty when assembled, but also one with a severe past.

Each casing tells a story, he said.

"And it's not very visible. By reading the markings on the base of the bullet casings and tracing the origin, you can see part of the history of the place — the war, violence and military interventions," Martinez said, as he secured strings of casings using a loom at Makers' Mill in North Adams.

Martinez has created other casing rugs. He has crafted similar projects in New York City, Lebanon and Guatemala.

It's a labor-intensive, exacting and tedious process: Going casing by casing, string by string, and tying off the ends of every row.

Martinez must get quite close to the casing to do the work. It gives him time to think.

"You can see where the casings have come from and what countries have been supplying weapons," Martinez said. "In Guatemala, for example, the casings came from Israel, which was involved in training their military. In the Middle East, the shells can tell us what countries have been supplying weapons to people in the area, like the USSR and the USA."

The project was aided by Assets for Artists, a Mass MoCA initiative that gives artists logistical support to create a specific project. Typically, Assets for Artists provide living space and studio space for a few weeks. For Martinez, the studio space was at Makers' Mill, a Main Street storefront that provides artisans with the tools they need, such as looms.

According to Kate Barber, chairwoman of the board of Makers' Mill, Martinez needed a larger size loom to handle his work, which was part of what attracted Martinez to the area.

"His work is really interesting," she said. "Especially when you consider the intersection of Mass MoCA, Maker's Mill and the community that made the project possible. The piece is beautiful, and he was just awesome. It's been great."

After drilling a hole through the sides and polishing each bullet casing, Martinez runs a string through them. Then he weaves each string into the rug on the loom. After three weeks and 15,000 bullet shells, Martinez has a brass rug that measures 4 feet by 8 feet. He said it is possible the rug might be exhibited locally.

Here in Massachusetts, Martinez faced an interesting challenge in procuring so many casings legally. Authorities regulate ammunition carefully, and until the holes are drilled into the casings, they could be re-used as actual bullets. It was a process that taught him much about gun culture and regulation in the U.S.

In other parts of the world, he said, supply wasn't an issue.

"Unfortunately, there is no shortage of material in some places," he said. "There's as much as you want."

The process wound up delaying the project a bit, but he and a friend were able to procure enough shells from shooting ranges in both Massachusetts and New York to complete the project earlier this month, the third week of his artist's residency with Assets for Artists.

Martinez said the bullet casings don't have much to tell about regional geopolitics here, but plenty to say about the economics and culture and economics of guns in the U.S.

On April 11, 1986, in Miami, eight FBI agents faced down two bank robbers. Two FBI agents were killed, five were wounded. The two suspects were also killed. But even though the FBI outnumbering the suspects 4 to 1, the agents were pinned down by opposing fire. Both suspects were hit multiple times during the firefight, but continued to fire on the agents.

The FBI blamed the poor "stopping power" of their .38 caliber and 9mm handguns.

So with Smith & Wesson and Winchester, the FBI engaged in a secret project to develop better defensive ammunition. They came up with the .40 caliber bullet, which was introduced in 1990.

"They needed something that kills people faster," Martinez said. "Bigger bullets make bigger holes, so the person bleeds out faster and dies faster."

He said the events depict the approach the U.S. has been taking with firearms.

"Rather than constricting access to weapons, they went with bigger bullets," he said. "It also tells an interesting story about the economics and techniques involved in killing people."