Before one can believe cryogenics improves barrels, one needs a coherent explanation of why it works involving properties that can be measured or seen, not just hand waved about. For example, if you think it changes the grain structure, well, grain structure can be photographed. Don't just hand wave about it, take a picture.
There are more than enough accuracy problems associated with the dimensions of the receiver and barrel, external forces on the system, and the timing of loads:
- receiver and bolt faces out of true
- barrels and receivers not drilled or threaded centered and true
- chambers too big, out of round, or off center
- all sorts of tool marks
- barrels that aren't drilled straight or that have been bent out of straight
- barrel tight spots that swage down bullets and cause gas blow-by
- muzzle erosion and cleaning damage that causes gas blow-by
- throat dimensions that cause a non-straight bullet start
- loads that exit the barrel on an anti-node and suffer gas blow-by
- inconsistent forces applied by things other than the receiver touching the barrel (stocks, bands, the shooter's hands and shoulder etc.)
- inconsistent burn
I have yet to see any evidence that in the absence of the above problems, barrel "stress" is a major issue. I have seen that when presented with a rifle that won't shoot (or walks), if you go over it you will consistently find the above problems.