While I use headspace gauges most of the time, there has been the occasion where doing something like a wildcat or even some of my target rifles can be properly set using sized cases. If done properly, there is no issues re-sizing and bumping shoulders.
For a test, the last 6br barrel I put on one of my rifles I set off a brand new piece of lapua brass. Very slight tension on the bolt close, tested with go and no-go and it was perfect. Reliable, no, but that instance it worked out perfectly. It can be done, but you have to know where you are at with your brass and how much of a bump you are able to obtain from whatever piece of brass you are using.
In the long run, its much easier, quicker and less measuring by just using gauges.
For a test, the last 6br barrel I put on one of my rifles I set off a brand new piece of lapua brass. Very slight tension on the bolt close, tested with go and no-go and it was perfect. Reliable, no, but that instance it worked out perfectly. It can be done, but you have to know where you are at with your brass and how much of a bump you are able to obtain from whatever piece of brass you are using.
In the long run, its much easier, quicker and less measuring by just using gauges.