After the knife, one of the most notable symbols to emerge from six months of Palestinian attacks in Israel and the West Bank has been the “Carlo,” otherwise known as the Carl Gustav submachine gun.

The homemade or craft-produced rudimentary automatic weapon has been used in the majority of shooting attacks on Israeli civilians and security personnel. It’s not accurate and it has a limited range, but it’s cheap and more than powerful enough to cause mayhem and death — and it’s nearly impossible to prevent its production.

These improvised guns were used last Wednesday in a shooting attack on a public bus and in the ensuing firefight with police, which left one civilian seriously injured; they were used a day earlier in a drive-by shooting that left two police officers seriously wounded; and they were used to kill 19-year-old Border Police officer Hadar Cohen last month. All of these attacks took place in or near Jerusalem’s Old City.

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Over the past few weeks, Israeli security forces have had some success in cracking down on these weapons, locating three small-scale production and storage facilities in the West Bank.

On Tuesday, the Israel Police and IDF raided a gunsmith operation in al-Sawahra, outside of Jerusalem, and seized a drill press that had allegedly been used to make weapons. And earlier this month, the Shin Bet and the army raided two other gunsmith operations, one in Nablus and the other in Jenin.

“There has been an expanded effort to seize illegal weapons that pose a concrete and lethal threat to Israeli civilians and security forces,” an army spokesperson said.

But nothing has been done so far to seriously curb the creation and proliferation of these homemade guns.

While some more advanced rifles and firearms require specialized tools, the Carlo has remained so popular because of how little machinery and technical know-how is required to produce it, according to N.R. Jenzen-Jones, director of Armament Research Services (ARES), a specialized technical intelligence consultancy.

A drill press, some welding equipment and blueprints from the internet are all that’s needed to create one of these potentially devastating weapons, a fact that presents a real challenge for Israel and countries around the world that are trying to prevent such guns from winding up in the hands of terrorists and criminals.

Swedish beginnings

The Carlo, as it is known, derives its name from the Carl Gustav m/45 submachine gun, a design that was adopted by the Swedish army in 1945 and later licensed to Egypt, where units were sold under the names Port Said and Akaba, according to a forthcoming report authored by ARES for the Small Arms Survey, a Geneva-based research institute.

But a “passing visual similarity” is where the connection between the Carlo submachine gun and the semi-automatic Carl Gustav rifles end, the report said.

Most of the current Carlos are based on designs from “American publications, which were readily available via mail order services, particularly during the 1970s and 1980s,” Jenzen-Jones told The Times of Israel over the phone.

“Today, designs are widely available on the internet, and are often shared among non-state actors along ideological lines,” he said.

The weapon’s mechanics are relatively simple: When a bullet is fired, the explosion blows back the bolt, which ejects the spent cartridge case and automatically feeds the next round into the chamber.

That process repeats automatically for as long as the shooter holds down the trigger, or until the ammunition runs out.

But outside of this simple design, the Carlo can vary in both appearance and operation. “One of the most widely observed iterations of the ‘Carlo’ design is easily distinguished by the inclusion of a commercially-made M4/M16 style pistol grip and the use of 9 x 19 mm Uzi submachine gun magazines,” according to the ARES report for Small Arms Survey.

But others have apparently been modeled after Heckler & Koch MP5 submachine guns and AK-type assault rifles.

The use of such designs “may serve an information warfare [propaganda] purpose,” according to the ARES report, making homemade knockoffs look like the real deal.

In addition to taking on various outward appearances, the guns can also be adapted to suit whatever kind of ammunition is available. “‘Carlo’ submachine guns are most commonly chambered for the ubiquitous 9 x 19mm handgun cartridge,” according to the forthcoming ARES report.

However, there have also been examples of versions that work with “other calibers, including .22 LR, .32 ACP, 9 x 18 mm, and 5.56 x 45 mm.”

Inaccurate, but cheap

Deadly as they have been, Carlos are not good guns by any technical metric.

“It’s a very basic firearm design, with limited utility,” Jenzen-Jones said. “They’re often smoothbore weapons, which means their accuracy is very limited, their range is very limited.”

In order to improve the accuracy and range of firearms, during the 18th century gunsmiths began “rifling” their barrels, putting grooves on the inside that made the bullet spin as it exited the gun, a process that stabilized the projectile and allowed it to travel further. (Americans, think of throwing a football.)

Smoothbore weapons, however, don’t have that spin. So — like the muskets of old — in order to use them, one must get closer to the target.

‘Their accuracy is very limited, their range is very limited’

The benefit to these smoothbore guns is they don’t require the specialty equipment necessary to create internal grooves in the barrel, which makes it both cheaper and easier to craft them.

For instance, the barrel of one of the guns used to kill Hadar Cohen in February reportedly came from a commercially available water pipe.

“That’s not always the case, and there are some examples with rifled barrels,” Jenzen-Jones said.

Superior accuracy and range comes with a cost. A simple, smoothbore Carlo submachine gun can cost just a few thousand shekels, according to a senior IDF official from the Central Command.

Better versions of the Carlo, including one that features a rifled barrel for greater accuracy, can cost NIS 10,000-15,000 ($2,500-3,800), the officer said.

“This is a gun that can cost between NIS 3,000 ($769) and NIS 10,000. If you steal one car, you can buy two guns — not one,” the officer said.

In comparison, a real M-16 can cost between NIS 60,000 ($15,000) and NIS 80,000 ($20,500) in the West Bank, he said.

A global issue

Its simple design, low price point and ease of production has made the Carlo popular not only in Israel but around the globe.

“These types of craft-produced submachine guns have been documented all over the world, with criminal groups and non-state actors,” Jenzen-Jones said.

They have been found in “Croatia, Brazil, Chile, Ukraine, Italy, South America, the Caribbean, Australia” — and, of course, Israel.

Here, it is believed that these guns are being produced by “one or more illicit manufacturing operations with access to a capable distribution network,” according to the forthcoming ARES report.

But weapons of this sort can also be produced by one person or a small number of people in a house or private machine shop, which leaves fewer clues for intelligence services to pick up on than if the production required a factory or larger-scale manufacturing process.

“In other countries, we most commonly see submachine guns of this type produced by small groups of two to four individuals,” Jenzen-Jones said.

“There are sometimes smaller operations. There was a jeweler in Australia who made up to 100 weapons over a period of time,” he said.

The untraceable gun

Tracking down such guns once they’re produced is also no small task. Firearms, for all their deadliness, are relatively small and can be hidden easily, in houses or the wheel-well of a car.

In one of the IDF’s busts this month, a stash of 15 guns was found hidden behind a plaster wall.

The guns’ owner had been previously arrested and had revealed their locations during an interrogation, the Shin Bet said.

If he hadn’t, those guns — which weren’t visible or readily accessible — would have remained hidden, the senior Central Command officer said.

“Even if I knew that in the house there were guns, I wouldn’t have been able to find them myself. They were hidden behind a plaster wall. There was no way to get to the guns other than breaking through the wall,” he said.

Because of the benign and predominantly non-military uses for the machinery needed to create such weapons, rooting out their manufacturers is something of a lost cause.

Inspecting machinery suspected to have been used for this purpose would not necessarily reveal any concrete evidence, Jenzen-Jones said.

“In many cases, it is hard to attribute tools that people might have to firearms manufacturing in particular,” he said. Still, he added, “Israel’s security forces have a very good intelligence network. They’ve successfully tracked down and targeted weapons factories — for rockets and other improvised weapons, including these types of craft-produced firearms.”

The limited technical know-how and equipment required also means that replacement manufacturers can spring up as quickly as Israel makes arrests.

But as more shooting attacks occur, the country’s security forces will have no choice but to put more emphasis on finding these Carlos and arresting their creators — Sisyphean though that task may prove to be.