Accounts that I have read seem to suggest that this was as more a sport activity than merely a crow cull.
The "rooks" were juvenile crows sitting on branches - and referred to as "branchers".

This rooking was done before the 22rf became popular as I understand.
The slow bullet was likely preferred for a short carry.
YMMV.


Dumb, but learning...Prof Em, BSc(ME), CAE (FYI)