so larcher take a look into this and the bolt head was changed for accepting the bigger rim of the Gras case. that makes sense so any kind of 11mm Gras ammo at hand was working in this rifle including old blackpowder ammo. I dont thought this before when seeing the pic of the bolt head because it was looking unchanged but we all make mistakes. far and away in the colonys its is a good thing to use any ammo you can get. they have shoot the rifle here only with nitro for black loads but I am sure there were Grasset made rounds with a higher velocity.
when the rifle was shoot for the article .458 bullets between 300 and 500 grains were pressed down to .445.

thanks larcher