Thanks for the tip, I'll check out Liberty Tree. I thought I had trouble getting them to ship to Canada, but maybe I am mis-remembering.
We had a little trouble with ignition on smokeless powder, ended up going with Hodgdon FFFG black powder, 20 grains by volume. Made me feel a little safer working with lower pressure black powder. Also the FFFG while messy, isn't really corrosive. Sealed off the cartridge using hand soap. It ain't fancy, or field tough, but it works haha.
At a high angle it lobs my grenade 100-120 meters, lots of fun.
Amazing that the sights on that MAS-36/51 can be set to a max range of 380 meters!!! That is one serious charge in that grenade launching blank, and must have produced some extreme recoil. No wonder they were cracking stocks.