When Google updated its Site Move Help documentation in June, webmasters had doubts on why Google recommended 302 redirects in the "Moving from separate URLs to same URLs" scenario. Google guidelines said, “Redirect your separate smartphone URLs to your desktop URLs using server-side 302 HTTP redirects." Google has once again updated the guidelines, now saying "Redirect your separate smartphone URLs to your desktop URLs using server-side 301 HTTP redirects."
The news was first reported by Aleyda Solis on her Google+ page. Here’s a screenshot of the older and newer versions of the recommendations taken by Aleyda:
There has also been changes in the “Moving from same URLs to separate URLs" scenario. Google earlier recommended "using server-side 302 HTTP redirects" but now is asking you to use server-side 301 or 302 HTTP redirects.Google now Recommends using 301 for Mobile Redirects!,