Actually this guy is somewhat right. It doesnt actually melt the barrel but rapid fire does heat up the inner surface of the barrel quite fast. Doing this in rapid succession heats the inner surface faster than the heat dissapates to the rest of the barrel. This is enough to soften the metal inner surface enough to permanently effect accuracy.
Take a second to think about what the **** you just said.
This is a device that has taken thousands of years to even conceptualize, it shoots projectiles using chemical reactions at hundreds of miles per hour, and you think that they'd make it so you'd literally have to cool it in water after four shots or it would melt.
you ******* walnuts this has nothing to do with cooling and everything to do with the fact that they are demonstrating that the weapon will work perfectly well in a variety of conditions including being submerged in water.
Holy **** people he isn't doing it to cool the gun down he is showing it is functional by firing it then puts it in water to fire it again to show durability of the weapon that's it.