Throwing a hand grenade

There’s a small opening directly in front of the soldier who drops it, I assume it then rolls into the main pit from that.

No idea what the purpose of the exercise would be if genuine, possibly a means of building trust among comrades, but pretty extreme if it is.

Also smothering a grenade with a helmet isn’t always as bad an idea as you might think, this Medal of Honor recipient did it and is still alive to this day:

A few years ago, thanks to modern body armor and dropping onto the grenade backpack-first instead of belly-first, a British Marine survived covering a grenade with his body, receiving only a nosebleed and perforated eardrums. He was awarded the George Cross in 2008.

An one would think that the current Kevlar/composite helmets would be even better than the old steel pot at this.

Yeah, but then again they’re going to give you a medal of conspicuous bravery for that sort of stuff anyway :p. What else are they going to write, “Pvt Smith heroically curled around the grenade and was subsequently scattered over his entire platoon, which had opted for a more sensible course of action consisting in hitting the deck behind cover. That was remarkably retarded of Pvt Smith.” ?

Having an controlled experimental data point is probably more definitive proof than a bunch of adrenalined up guys going “OMG he totally saved our lives !!” over and over, you know ?