The M8 will definetly fit in a C8 holster and will be way to big for a M8.
By the way there is another light that is even smaller than a M8 but puts out about as many lumens if not more and throws as far for a fact, and it’s on sale right now I noticed… BLF X5


BLF X5


The M8 barely fits their holster but it works and is clean looking.

M8 about 75 yards to the wall