The RWS sighting-in target is optimal for this use and can be downloaded here.
RWS is well known for the fact that points of impact hardly change from lot to lot.
Still, it is necessary to take a few control shots to be sure that nothing has changed when switching ammunition lot numbers.
RWS Target
RWS HUB Day Target
Here you can find the two targets of the RWS HUB Day, which were used in the competition.
You can download, print and use the targets for your own competition.