Fort Gertrude!

The Imperial engineer, Major Dougal Entendre, stands in one of the gun positions of the newly constructed Fort Gertrude. With him is the commander of the fort, Captain Stefan Andreas von Dreihumpe.
'Try again, laddie. Look carefully, captain,' Entendre is saying to Dreihumpe, 'and tell me what is wrong with this gun.'
Captain Dreihumpe peers intently at the  gun for a long time, his face working itself back and forth like King Wilhelm's belly at a royal dance. 'Is the gun ... the wrong colour?'
'Nae captain,' says Entendre, slowly. 'The problem I think that we face here is that yon cannon in front of us is only this high,' he says placing his hand at the level of the barrel. 'Whereas the embrasure for the gun is this high,' he says placing his hand rather higher. 'And that means that ...?'
'It's well protectetd from enemy fire?' says the captain hopefully.
'Yes,' says the engineer patiently. 'Yes it is. But don't you think laddie that it's also likely to reduce the range of the cannon somewhat?'
'Oh. Oh yes,' says the captain, nodding. 'It is likely to cut it a tad.'
'Yes,' says the engineer. 'And by a tad, I think that we could guess reliably that its range would be reduced from, say, around 800 yards with round shot, to about,' he measures with his fingers, 'six inches.'
Dreihumpe contemplates the situation glumly. 'Now I think about it,' he says, 'I can see that that might prove to be challenging for the gunners. If they tried to fire a round of canister they might do themselves a bit of a mischief.'
The engineer nods. 'Aye, if by "a mischief" ye mean that they might blow their own limbs off then I think yev diagnosed the problem correctly.'

'So what might be the solution,' continues the engineer slowly as if to a small and, characteristically for Mittelheim also very inebriated, child. 'If this gun is too small for the embrasure then we could do what?'
'We could ... we could ...,' replies the captain, searching Entendre's face for some small hint to the answer, 'we could ... lower the height of the bastion?'
'Aye,' says Entendre, 'but that might take a great deal of time and effort, as well as wearing out my patience, breaking my temper, and requiring ye to take a great deal of time convalescing from the pistol shot to yer head.'
'Pistol shot to my head?'
'Aye, yes - to be more specific: my pistol shot to yer head.'
'Oh.'
'So, if we don't lower the height of the bastion, then we could ...?'
The captain pauses for a moment, thinking very hard indeed - suddenly, he brightens. 'We could get a bigger gun!'
Entendre smiles broadly and also discretely returns his pistol to its holster. 'Excellent idea, captain. Give the orders!'
A larger gun is duly installed. This, as it turns out, is fortuitous because for the Fenwickian garrison the next day turns out to be dry, sunny, with a good chance of some intermittent Gelderland assault columns ...