could possibly be that they were not resized properly.
check how the resizing die is on your press, should be kissing the shell holder and a tiny bit more.
double check after you deprime and resize, before repriming.
the bullet should fit very snug tight, if not something is the mater in the resizing process.
check list of some common things that can cause this:
die not set all the way down
did not go though full down stroke on the press in the resizing process.
incorrect die used (been there done that)
incorrect diam' bullet used (been there done that).
these are just a few things that can happen, we would need more info in order to help you out.