The code you provided works as expected on a fresh install of WordPress (4.3.1 in this case). The ideas below shouldn’t be considered an answer, so much as a checklist to aid in debugging the issue by narrowing the scope of the problem:
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You’ll need to be logged in as a user with permission to view drafs to avoid a 404 or redirect.
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Try disabling your plugins one by one to see if perhaps one of the plugins has established a conflicting rewrite rule.
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Check your web server configuration (such as .htaccess on Apache) to see if there are any redirect rules in place there.
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Finally, consider temporarily switching to another theme and adding your custom post type there to see if you get the same results. If a new theme solves the issue with your code, perhaps the conflicts all exist within your current theme.