Thread: full size vs neck size

So I had a packet of federal orange packet stuff for the 300wsm, once fired it left small extractor marks, anyway I neck sized them and they were really hard to chamber.
I got some norma brass and loaded it up then once fired I neck sized and they went in sweet as. Why?

Should add once I shot off those tight reloads from the federal brass I put them through the full length size die and neck sized after those ones had been shot and its fine.