My daughter has been checking the nest boxes daily for almost 3 weeks for the first egg. We went on holiday - the day we went they laid 3! The white leghorns eggs have started larger than the full size the banty eggs ever got to. They are medium to large in size. Hopefully the black rocks will be similar when they start in a month or so. The day we returned I got my mate to lay the eggs out in the nest boxes so she could find the first egg......
Checked my chicken breeding book and apparently hens eggs are full size when the hen reaches 30 weeks. So hopefully by then all eggs will be large.