Dave, the headspace is the play between where the shoulder meets the front of the chamber and the base of the case meets the bolt face in your cartridge. Thus, if you keep full length sizing the case you continue to excessively push the shoulder back towards the base of the case which continually causes the case to grow forward with each firing. This causes the thinning of the case wall resulting in head seperation. Once full length sized, and fired it stretches to fit the chamber perfectly. At this point to stop the case from growing, lenghtwise, and thinning the case wall you need to neck size only or throw away the case once it no longer chambers easily. Further, once the case does not chamber anymore comfortably, it is time for other options or disposal as mentioned.....Which brings me to the point of, it is time for you to get a good manual and learn how to bump the shoulder back just enough to fit the chamber again. M.L. Mcphersons reloading book is good, so are the reloading videos that are put out by varmint hunter magazine....I am just looking out for your safety not preaching to you.....That is scary what happened especially with such a mild caliber.