I decided to finish loading up some 308 precision rounds this weekend that I had begun working on several weeks ago. 80 cases were Federal that were previously fired in my SPS that were neck sized only; 15 cases were RPU that were FL sized that I wanted to run as an experiment (how much of a group difference would they make as compared to the cases previously fired thru the SPS). What I found while loading the 168gr SMKs was that there was a very noticable difference in the neck tension between the FL and neck-only sized cases. The neck sized cases (Lee collet die) had just barely enough tension to hold the bullets - adequate, but not nearly as tight as the FL sized cases (RCBS). This should add some additional insight on how these neck sized rounds shoot. The cases previously fired in the SPS were new Federal brass that was initially prepped by FL sizing during the loading. They were able to give me a five shot .583 grouping (100yds) during load development. I know Steve is going to jump in here and offer up that I should have taken multiple ID and OD measurements. I now think that doing so could have been rather informative. Maybe I'll go out and take some readings on other once-shot brass later on tonight. Has anyone else noticed any differences in neck tension between neck sizing dies and FL dies?