Ello,
Assuming your firing solution is correct
- point your periscope until gyro angle says 000
- open tubes
- wait for the part of the ship you want to hit to be at the angle your periscope is at (gyro angle still 000), and shoot.
+/- 10 degrees each way seems to work fine too, so technically you could aim yourself just by pointing the periscope within that threshold for multiple torps if firing them individually rather than salvo.
I'm still quite new to manual targeting though, so I haven't tried to stretch beyond +/- 10 degrees. But the above seems to be deadly accurate every single time (assuming correct calculations)
- Edit - GWX3 here also.