The cartridge of choice....
For rural areas in an essentially urban environment like you're in, the .222 would be a very good way to go. Blast is considerably less than the bigger cartridges, and the round runs at 46,000 psi rather than the 55-60,000 psi of the .223s and .243s. Much longer barrel life with the smaller powder charge and lower pressure makes this very attractive to those of us who have to pay for our own repairs.
Another choice would be the old .22 Hornet, but ammunition is not as readily available in that chambering. The .22-250 is another good round, but loud and hard on barrels. Since you are in Europe, I suspect there are some pretty tight strictures on loading your own ammunition for whatever you wind up with. If you will give me some rundown on your laws, I will be happy to help you figure out what to look for.
There is another site in this ring, Military Small Arms Restoration Corner, with a very knowledgeble fellow, KevinP UK, who runs the reloading and shotgun parts of the forum. He could, perhaps, give you even better guidance. Good luck in your search.
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