In reply to:

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If you are asking how accurate a Double should be I would say minimum of 3" at 100 yards. Anything less is useless and needs to be fixed. This can be by changing the loading or getting the rifle re regulated.

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By that logic, then the group below is useless and should be "worked on" or re-regulated?

This is only a 2.5" at 50-yards, which would no doubt be larger than the noted 3" at 100.