Why?

I love this movie, but there are several plot holes in it. One that is very strange to me is when Lomax and Billy break into the powder shack to steal nitro from Pierce's stock. Why does Lomax and Billy bring empty whiskey bottles with them to transport the nitro when they could just take the nitro in the original bottles and not have to take the chance of pouring it from one bottle to another? That would be a risk that would be foolish, IMHO.