With Grey Wolves, manual targeting, no WO help, I am getting about
-15 to 60 thousand tons per patrol.
12k is the lowest, 60k the highest. Usually 20 to 30k.
I sunk ships every patrol.
My patrols have been short: less than 18 days, because I have been throwing all my torpedoes at convoys and resupply has not been convenient.
I have sunk ships with 1 torpedo, especially tankers, but I usually have to work quite hard to sink all other kinds. (One medium tanker last patrol seemed unsinkable. 4 torpedoes. Bad waves. Waited forever. No sinking.)
I really like the realism of this. (Sinking variability.) It seems right.