Possible Clues:

• Contracts for northern shafts
• Not, broadly speaking, shafts of the North
• It gets shot from pole to pole, but not broadly speaking
• Channel dominated essentially by darts
• Oars used by sailors going back across a stretch of river
• Contracts speeded up arguments
• Gets smaller new missiles
• On reflection, rushed argument's sound?
• Squeezed between poles, shaft becomes smaller
• Pointers after end of construction contracts