I’m assuming the sub won’t be beached or take the risk to run aground, so it will have to keep some distance to land, 1500 meter is a paltry range.

We’ve only established it has been tested out to 1500m and proven effective. We’ve not established that is the max. range or even the max. effective range. Besides, SFO not only deal with land targets, so why are you assuming that for the gun?