In The Walking Dead, [S4E8: Too Far Gone](http://www.imdb.com/title/tt2948638/), Daryl takes a grenade and tosses it down the barrel of a tank. After a few seconds when you hear it bouncing around, some people abandon the cockpit and then it explodes.

Would that actually happen? It seems like a pretty flawed design if something hostile could make its way in and do that. Obviously it's a completely different machine, but in a semi-automatic pistol, for example, a foreign thing would never be able to make its way completely through the barrel because a round is already loaded in the chamber.

So is this just cinematic drama?