Unfortunately, you can't depend on your in-camera meter when using B&W filters. Some meters are more sensitive to different colours. One camera may show the correct reading, whilst another may show a considerably different reading. I've gotten into the habit of checking my camera's metering before going out to shoot by holding the filter up to the lens and verifying things first. On my Nikon FG, I get a good reading w/ a yellow filter, but orange and red filters require a manual adjustment to get things right. On my Nikkormat, I can let the camera's meter handle things most times, but I still check it beforehand out of habit.
For my next trick, I will reply to a thread that's well over 5 years old.