after researching this, the ammo is not sub-par. It's designed, and tested by major ammo company's who are not in the business of wounding game. 99% of the reviews are 1 shot kills.

I've seen more reports of guys losing game with a 12 ga slug.
IIRC, I read just one review about a guy who said the M-R bullet didn't preform, and he lost the deer.