That once fired brass was fired in that rifle with it's current headspace?
If that's the case, and you have some concern that some of the brass might be a bit tight during rapid fire if it's only knecksized (which is common), then I guess the thing to do would be to use a FL die adjusted down only to the point where the brass offers no resistance when the bolt is turned down.
While I segregate and knecksize my 303 brass to a given rifle, I do lightly bump the shoulder about every three loadings. I can't see where such practice has shortened case life to a noticeable degree.