I was wondering what would be the best marking substance. Paint would be messy to work with, I didn't try using it. Instead I turned my addension on to flour. So I did some tests. First, earlyer in the day I put some metal fittings together in an over & under design with a ball valve and a piece of metal pipe as the barrel. The ball valve will be spring loaded with tension springs, and a sensitive catch mechanism to trigger it. (pic down the page)
I tested it with flour rammed down the barrel and fired it manually, the trigger is not yet built, the results were ok. It managed to fire flour in a big cloud.
A test I did recently involved my shotgun(yes I found a pump), I filled the barrel with flour, toilet paper behind it all, and fired. At about 40 psi (no pressure gauge). Heres a video of the results.

I will psot designs of the bazooka and mortor later.
I think flour could be used as a harmless marking substance and can be used in landmines. I am not sure about the grenades but you guys post whatever ideas you have.