From what I understand about R-Guns from another Forum, is that they're using 8620 Steel because it's easier to get, instead of the (now) recommended C-158 Steel. Heard that lots of the (better) Manufacturer's were having hard time getting C158 Steel, and that's why you're seeing "out of the woodwork" cheaper BCG's on the market.
Considering this, how would Cryo help? I know it changes the molecular structure, but every break I've seen on a Bolt is at the Lugs which is the weakest link. Good Steel or Bad, if it's a weak link anyway, where would the savings be?