I use MK 27s all the time in late war and all my tubes are loaded with them,however i have altered the speed of my mk27s to about 30knots and a range of about 5000.you can alter the depth as mentioned before to what you want your torpedoes fo fire at.
I know launching these little fish at pd can be lethal not just to the enemy but to yourself as a found out a few times.
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