Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the bore of the boat howitzers with a 12-pdr heavy designation?

### Inputs:
table_name: table, columns: ['Designation', 'Bore', 'Weight', 'Service Charge', 'Range (yards)', 'Number Made']

### Response:
SELECT Bore FROM table WHERE Designation = 12-pdr heavy