Greg, thank you for your info. They are actually Blondeau and are being sent from France.
Knowing the name I did some searching and found that there is a newer version with a plastic sabot that can be shot even through full choke barrels. It should be safer.
As to locally available powders, I have to gather more information. All I have for now is what is in a catalogue of the local Fiocchi agents that have only one type (described as being of the "simple base" type) and say that a charge between 1,5g and 1,6g should be used in a 12ga. shotshell with 32g of shot.
You will gather that I am totally new to the reloading science and also very aware that a lot of care should be excercised (I have no redundant body parts). 
Do you think one could replace the shot charge of a factory loaded shell with this type of slug? If so, how would one go about it?
Thanks in advance.
JC(AL)