Upon detonation, the M-84 flash bang grenade emits an intense, Metallica-loud “bang” of 180 decibels and a blinding flash of a million candle power (more than 1,000 lumens) within 1.5 meters (or around five feet).

Say Goodbye to Your Ears

Once, we had a few flash bang grenades left over from a training operation with SEAL Team Three, so we decided to light a few off in my neighborhood near San Diego State one Halloween evening.
I was a new guy with GOLF platoon and had used a few flash bang grenades in training in the desert but had no idea how loud they were in an urban setting outdoors. We shattered one of my window panes and set off every car alarm within a block’s radius. Then promptly went inside before the cops came! “Holy s***!” we all muttered. The bang in a close urban environment with no hearing protection was no joke!

Common Questions About the Flash Bang Grenade

1. Can a Flash Bang Grenade Kill You?

It is possible, although in most cases it will just mess you up for a while. The M-84 has a thin aluminum casing filled with a magnesium-based pyrotechnic charge. Its thin case is itself inside a perforated cast-steel body. The detonation of this pyrotechnic charge produces a subsonic deflagration, rather than a supersonic detonation. This is not enough to turn the grenade’s steel body into flying shrapnel, thus minimizing its lethality. All bets are off, though, if you were dumb enough to pop one off right next to your own head.

2. Can Civilians Purchase Flash Bang Grenades?

Yes, but not military-grade grenades unless you are buying them illegally.

Iraqi commandos train using flash bang grenades.
Total chaos: trainers at the Iraqi Special Warfare Center Commando Course use flash bang grenade simulators to create an atmosphere of chaos and encourage teamwork. (Photo by Spc. Spencer Case/207th Public Affairs Detachment)

3. How Does a Flash Bang Grenade Work?

The main idea is that entry teams will crack the door open, roll in a flash bang or two, and BOOM! BOOM!
Whoever is in the room is temporarily stunned, blinded, disoriented, and ears ringing. The entry team flows into the room, one left, one right, etc. clearing it of hostiles. It then moves on to the next room and repeats the process. The flash bang is very useful for room clearing and gaining a massive advantage over the enemy.
As described above, mechanically they work like any other grenade does, except the charge is much weaker and the casing is not designed to punch holes in you with steel fragments.
It is said that the British SAS developed the modern stun grenade in the 1960s, but it was probably the Germans in WWI.  The German Stielhandgranate or “stick grenade” was more of a stun grenade than a true fragmentation type. Its metal casing was as thin as a soup can. This is why we read stories about American GIs surviving after throwing themselves onto a German Potato Masher.
Stielhandgranaten. The Germans were probably the ones who first developed the stun grenade.
Two First World War Stielhandgranaten on the left. One the right an Austro-Hungarian grenade is visible. (Wikipedia)

Flash Bangs Versus Pirates

The regular Navy was initially tasked with boarding these ships and steering them down to the United Arab Emirates. But the smugglers caught on fast and started welding the hatches shut so the boarding teams couldn’t gain entry. The boats hauled ass for Iranian waters and the teams were embarrassingly forced to deboard the ships. Bring in the SEAL Teams…
A welded door or hatch wasn’t going to stop us. Our platoon would slither aboard at night, sometimes climbing a caving ladder 30 feet with full kit, and always with the element of surprise.
One team to aft steering and one to the bridge, both critical for control of the ship.
The bridge team would send a breacher with an oxygen-powered cutting torch to the bridge’s rooftop to start cutting a fresh hole. After all, cutting a fresh hole in the roof is much easier than going through a welded door.
Flash bang grenades are commonly used by special operations units when boarding ships.
U.S. Navy SEALs board a vessel alongside the Lithuanian combat divers service, or KNT. The SEALs and the KNT worked together closely during Exercise Flaming Sword 20, Lithuania’s annual special operations exercise.
You should have seen the faces of these guys. Panic at the disco.
To lighten up the mood even more, once the hole was cut and the big steel circle fell with a thud to the floor of the bridge, you guessed it, we’d toss in a flash bang grenade (or three) to get the party started.
Most of the time half the smugglers on the bridge would crap their pants like a one-year-old kid who ate too much apple sauce. You don’t see that scene in Call of Duty! Within minutes the ship would be ours.
Doom on you bad guys.
Flash bangs are no joke.
Webb out.

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