The "force" to https could be handled in many ways so I can't say if it is a 301 redirect or not. But you can check: http://httpstatus.io/ .
http and https indicate two different URLs. That I know of, Google doesn't just automatically assume a one-to-one relationship between them and choose a canonical version for you if both are available to index. In other words, if users end up at https just go ahead and redirect straight to https. Really, if you're site is https you should just forget http even exists as an option. Even an internal text link with the wrong protocol can throw up errors in some browsers.
For what it's worth, I just switched one of my sites over and got burned by listening to Google once again. All went well from a technical perspective, except that revenue dropped by about 30% because Adsense is no longer showing certain types of ads (probably re targeting).
