Well, I just used it (running 1.5 TMO) and on a day so foggy you couldn't see the front of the boat, sank 2 destroyer escorts and 3 merchants. Had maybe 20 rounds left over out of 150, so I put them into the remaining three merchants with no effect.
Oh yeah at the range I was shooting them we could have played frisbee pretty easily.
Nice thing is. it was so foggy they couldn't shoot back!