It’s designed to look like a random mag which was left behind after a hasty retreat. If your Army uses Kalashnikovs, you might put it in your own weapon. If your Army doesn’t, you might strip the cartridges out to empty it for disposal. In either case, you took the bait!

This particular magazine was discovered by British troops in Operation Joint Endeavour, 1995-96, sitting on a trench mound. The grenade-type pin was still inserted which alarmed the Soldier who found it. Here’s how it works:

Once the pin is pulled, a detent switches from safe to armed. It cannot be switched back to safe at this point. There is a dummy cartridge at the bottom of the mag, so that if you look at the peep-hole indicator you will think the magazine is fully loaded. Also, the booby-trap weighs the same as a loaded magazine. The 5 rounds at the top are actually live, so you could fire or inspect those thinking nothing is abnormal… Until it’s too late.

As each live round is removed from the magazine the explosive sequence progresses. A spring-loaded striker is released upon the last round leaving the magazine. It strikes a detonator and unleashes the main charge of 35 grams TNT. For reference, that is ~62% of a WWII hand grenade (US Mk.II has 52 gram TNT / Russian F1 grenade 60g). In other words, 62% of a hand grenade explodes in your hands.

The magazine is a Russian AKM mag, however it says “Yugo” because Yugoslavia or Serbia created the booby trap. It has qualities of factory construction, rather than a one-off from an enterprising individual soldier