Oh! That's what I've been doing wrong this whole time! You're supposed to load a bullet in the damn thing!
Well that certainly explains the lack of blood trails.
"Lots of fragmentation" seems rather self explanatory, but since you asked, it means that plenty of little pieces are no longer attached to the bullet, which coincidentally, weighs a lot less if it is recovered. I have a sneaky suspicision that the low weight coincides with all those little pieces that are no longer attached. "lots" is entirely subjective, but I'd imagine based on gel testing something like a 77gr TMK or 75gr ELD is about half its starting weight at the end of its journey.
I've observed this phenomenon mainly with my eyes, and in deer I have shot with a couple 77gr match bullets, in deer that others have shot, and in gel tests that I have seen.
If I may ask, what does "quite simply devastating" mean? Especially compared to larger cartridges like 6.5 CM, 308 Win, etc?