Okay, on both shots there appears to be smoke or an impact slightly to the left of the cars and maybe behind them, then there is a delayed explosion, then the cars explode. I’m going visual, not sound. So I’m wondering what kind of shot is being used or if there is a separate charge rigged on the cars that are set off remotely, just to make everyone happy. In any case, though, it is exciting. Hate to face one on the battle field, especially during the Civil War. Messy.

The cars were hit, but they were remotely detonated as explained here.

https://www.youtube.com/watch?v=ytOWmfupUt8

There are competitions for Civil War cannons and mortars at various locations around the country every year. If you’re near one and you appreciate their history, it’s worth the time to check it out. Even the smooth bore cannon are accurate out to 600 yds. or so. Mortars are surprisinglyaccurate as well.
I shoot vintage rifle matches with some of these fellers:
http://www.robinsonsbattery.org/311134.html