JAR OPS states:
When carriage is allowed by the operator, cartridges for sporting weapons, providing they are in Division 1.4S (basically they have to be packaged, and any dangerous effect they have can be contained within in the packaging) they are for that person's own use, they are securely boxed and in quantities not exceeding 5kg gross mass and they are in
CHECKED BAGGAGE. Cartridges with incendiary or explosive projectiles are not permitted.

Good for the crew, bad for airport security!