BSA,
Have talked to several barrelmakers about cryogenics, and the consensus was that it didn't make any consistent difference (if any) after the barrels were done--but did help some with the blanks BEFORE they were drilled, reamed and rifled. But also know that at least one of those barrelmakers (a top-notch cut-rifling firm) eventually quit doing it, since it cost more time and money and didn't make enough consistent difference.
Cut rifling doesn't really add all that much stress anyway, not when compared to buttons and hammer forging.
