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.
