Ive got one of those wheeler digital fat wrenches and much like a breaker bar on a lug nut....my hand/arm calibration is way....waaaaayyyyyyy out it seems LOL.
Admittedly ive had nothing but bad experiences with crossfire2s, not in the functional sense but ive never been able to get one adjusted so i was comfortable. The DBs tho, while tight on eye relief and not very appealing to me have proven to be pretty reliable...again from the dozen or so that ive seen.
BUT Ive got a friend that had two Vipers fail exactly the same way, in exactly the same conditions. Vortex replaced both under warranty, but it ruined them for him. He gave the last replacement to another guy whom I dont know, so cant report on if it survives.
Ive seen a number of scopes fail, it happens. Personally ive had really good luck, the only scopes that have failed either came that way, or I squished them (or something similar).