Run a Google search on "H205 powder". You will come across another forum which has a thread that alludes to it being a pulldown powder and then links to this chart
See entry #197.
You have no way of determining if the original owner took some empty powder cans and filled them with a fast pistol powder or shotgun powder. I do a lot of stupid things in life and most of them could have been avoided if I had taken 10 seconds to think about it before I did it. I would suggest you take 10 seconds here and use your brain.