Hand grenades are designed to be thrown, so they are light. But when they are dropped from drones, this can be a drawback. With a typical weight of just 300 grams, grenades are short on “killing power”, says a man nicknamed “Lyosha”, who is an amateur weapons-maker based in Kyiv. After one goes off, he says, targeted Russian soldiers “often just keep running”.

Three months ago Lyosha and a group of friends, working in their homes, designed an alternative: an 800-gram anti-personnel bomb called the “Zaychyk”, or “Rabbit”. The group uses 3D printing to produce the bomb’s casing, before sending it to be filled with C4, an explosive, and pieces of steel shrapnel. In tests, Lyosha says, this shrapnel cuts into wooden planks “like butter”.

Necessity is the mother of invention, and the Zaychyk is but one example of the sorts of lethal innovation that have sprung up in Ukraine in the 17 months since Russia’s invasion. Stocks of many factory-built munitions have shrunk as the fighting has worn on. But raw explosives remain plentiful. That has helped create an amateur arms industry devoted to supplying soldiers at the front with improvised weapons to use against Russian troops.

Lyosha’s team prints the plastic shells of around 1,000 “candy bombs,” as these improvised explosive devices have come to be known, every week. But the Ukrainian officer who acts as the team’s military contact wants 1,500 a day, says “ADV”, the nom de guerre of a second member of the group. Another set of amateurs, the Druk (“Print”) Army, has churned out more than 30,000 candy bombs in the past four months. “Swat”, their leader, says that the production rate is growing. And still more come from beyond Ukraine’s borders. Janis Ozols is the founder of the Latvia chapter of the Wild Bees, a group of volunteer weaponsmiths from outside Ukraine. He reckons at least 65,000 bomb shells have been shipped from Europe since November 2022. (Ukrainian customs officials have turned a blind eye, classing such shipments as children’s toys or candle-holders.)

Improvised munitions are not a direct replacement for the factory-made sort. But they have advantages. For one thing, they are cheap. Emanuel Zmudzinski, a Wild Bees volunteer in Lodz, Poland, makes the components—a nose cone, body and tail fin—for a 27cm-tall model called the Big Egg for less than €3.50 ($3.85), not including the explosive contents, on a 3D printer that cost around $1,200. With no need to retool production lines, candy bombs can be readily produced in different sizes. That helps drone operators make the best use of a given model’s payload capacity.

Clever innovations have rendered the bombs surprisingly effective. Those designed to kill infantry incorporate a central cylinder into which explosives are packed. The space around it is filled with metal fragments, which will be hurled outward when the bomb detonates. In the early days many bombs used nails as shrapnel. But tests (which involved blasting the shrapnel into sheets of wood) revealed a shortcoming. The heat from the blast was partially vaporising the nails.

Bigger pieces of scrap are not vaporised, and so cause more grievous wounds. But irregular chunks of metal have unpredictable aerodynamics. Many were being flung either upwards, away from the target, or down into the ground—a waste, says ADV. Ball bearings are now preferred—though they are not cheap, and are in short supply. “Diuk”, a Ukrainian serviceman in Donetsk, a region partially occupied by Russian forces, says 5kg candy bombs are now killing exposed infantry 20 metres from where they land.

Bomb techies hope to extend the kill radius still further. Some “candy shops” use software to model the killing potential of different shrapnel types and mounting angles relative to the charge, says one soldier in Kyiv with knowledge of their efforts. ChatGPT, an AI language model, is also queried for engineering tips (suggesting that the efforts of OpenAI, ChatGPT’s creator, to prevent these sorts of queries are not working).

Some candy bombs can even be used against armoured vehicles. Copper and aluminium are pressed inside these bombs into a specially designed cone shape. When the explosives detonate, the metals are transformed into a thin jet of superheated plasma that can bore its way through armour. (The same technique is used by many commercially made anti-tank weapons.) Ukrainian drone operators claim to be able to destroy Russian tanks by dropping these bombs, which weigh around half a kilo, onto the vehicle’s roof, where the armour is thinner.

Diuk, the Ukrainian soldier in Donestk, reckons that his country’s military drones now drop around 200 different types and sizes of candy bombs. That is testament to their makers’ creative enthusiasm. But it also complicates supply lines, with components coming from several different workshops. An effort is therefore under way to reduce the variety of bombs and to standardise their production, says Mr Ozols, the Wild Bees organiser. An industry of amateurs is becoming more professional by the day.

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