Slugs

[ballisticboy]

Given that a decent diabolo in a decent barrel is capable of one-hole groups at 40 yards, how much more accuracy should we expect?

Diabolos will only give you a one hole group at 40 yards if you have managed to find the correct batch number and there is no wind blowing. But if you are happy to use the ammunition equivalent of a Model T Ford in your gun, albeit a well made Model T Ford, then that is fine. Other people are not.