Hi Bruno, the first thing to do is get a chrono & check that all your new guns are under 10joules. Then get the ones that are over declared to your prefecture via your local gendarmes using a form modelé n° 10 which you can find here
http://docs.google.com/viewer?a=v&q=...6cLM7ENezMEoDw
& before you do that you will have to have a Licence de tir (FFTir) valid for this year for any over 10J.
The guy that sold them to you should have done this, but has he?
Also unless laws have changed without me being aware, you are not allowed to hunt with air or gas.
Dave