Big no! In my limited experience every helmet seems to be different. I could fit a Large in one brand but not another. The helmet should be pushing your cheeks up a little and have no one spot tighter around your head than another, even pressure. The padding will get smaller over time, and in some helmets can be replaced.
That or your head grew between trying them and buying one
Eat any bad clams?
Felix
That or your head grew between trying them and buying one
Felix