There is an option present within Blogger settings (Under Settings 🡆 Basic 🡆 HTTPS 🡆 HTTPS redirect) which will allow you to set up 301 Redirects on a sitewide basis.
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If you want to prevent the round trip from HTTP to HTTPS without updating the post content for your users (won't work for crawlers), you will need to add the following meta tag in the <head> portion of the template code.
<meta content='upgrade-insecure-requests' http-equiv='Content-Security-Policy' />In case of a custom domain, you can also set up CloudFlare and use their Always Use HTTPS and Automatic HTTPS Rewrites features to setup 301 redirects.
