I have talked about this before but not sure if it has been made into a separate thread.

I'd like shooters of double rifles fitted with scopes to shoot their rifles say 1,2 and 1,2 at a target at the regulation distance. Photograph record note the results. Then remove the scope of put it on. And shoot the same 1,2 and 1,2, same ammo, same conditions and range. With no scope. Note, record, photograph. Note which was the regulated setup.

If you've got a red dot sight as well, or instead of a scope, use that in a third series as well. Or instead of the scope series, if the red dot can be removed easily.

It would be interesting to see how groups and regulation vary between open sights, red dots and scopes. Between whatever number of rifles.

Please give it a go and report back,