Only Russians, like the YouTuber Fire Domino, have the guts to pull off crazy experiments like this one!
The question is quite intriguing, though. When we think about a bullet being exposed to flames; numerous possibilities come to our minds. Would it blast off just like shooting a gun, or would it explode right on the spot? You may not know the answers to these questions, but we all can agree on one thing, that the end of this incident will be destruction.
However, in reality, the bullet goes off disappointingly in a passive way at 0:25, after expansion of the shell caused by the heating of powder.
When a bullet is put in the barrel, it has nowhere to go but out of the hole. But in the case of the video, the torch was held close to the bullet and thus, made a microscopic hole which was enough for the compression to fizzle out and not result in a flaming mess. The gasses inside the lead casing are clearly seen to emit by taking the path of least resistance as the powder is burnt off.
The fact is that even a big .50 BMG round filled with gunpowder would cause a few dents to the casing if put under similar conditions. The modern gunpowder is not an explosive, but rather a propellant. It burns quickly when in confined spaces under lots of pressure. But when left in the open, it doesn’t even burn fast and fizzles out while producing a lot of smoke. Hence, the anticlimactic results of the video!
https://www.youtube.com/watch?v=gmda_pHFx8Q