user: Question: If the gun used is the QF 12 pdr 12 cwt, what is the shell weight?
Columns: ['Gun', 'm/v ft/s', 'Shell (lb)', 'Time to ft (m) at 25° (seconds)', 'Time to ft (m) at 40° (seconds)', 'Time to ft (m) at 55° (seconds)', 'Max. height (ft)']
Types: ['text', 'real', 'text', 'text', 'text', 'text', 'real']
Sample row: ['QF 13 pdr 9 cwt', 1990.0, '12.5', '10.1', '15.5', '22.1', 19000.0]
SQL:

assistant: SELECT "Shell (lb)" FROM "Table" WHERE "Gun" = 'QF 12 pdr 12 cwt';