Thanks for the correction, Sig did call it a voluntary upgrade, not a recall. The do have other actual recalls, like on the Sig Cross rifle, so they are willing to do it when there is an issue that calls for it.
https://www.sigsauer.com/blog/safety-recall-notice-sig-sauer...
They would have been in a better spot today to defend the P320 if they had made it a mandatory recall, so they probably should have done it.
