All good info. I will work on this. Per one posters advice, I will also fire a few factory loads to see if they'll rechamber. I'm pretty sure I followed procedure using my RCBS FL sizing die. All of my gear is RCBS. My neck sizer is Lee. Are you saying that my neck sizing problems could be caused by using a RCBS shell holder with the Lee sizer? My neck sized cases drop into and out of a Lyman head space gauge easily, yet the casing won't chamber. Are you saying the Lee die and Lyman head space gauge are incompatible? I thought head space gauges were designed to prepare casings to fit in all factory chambers. I don't have a custom chamber. Thanks again. I've got some work to do. Hope to get this resolved so that I can reload and get on with the shooting.