Cannon. Mutton tallow was the traditional black powder of choice with the British Ordnance as it melts at a higher temperature than most other fats and, when made clean, keeps at room temperature in a sealed container. Lard, made from cow, horse or pig will melt more easily at hot day temperatures and go rancid far more easily. IIRC deer tallow also has the same property.
Easy to make with mutton/lamb fat offcuts. Remove any non fat bits, Set a pan of water to simmer. Add the fat cut up. When it has melted and covers the surface of the water turn off the heat and let it cool and the fat to harden on top of the water. Any remaining non fat bits will be on the bottom so carefully remove the fat, put in a fridge overnight then scrape off any iffy bits underneath. Then you can remelt it and pour into the container of your choice. Pop on a lid and it is ready to use. I am still using some I made a few years ago.