Thread: Case head separation

Greetings to all and thanks @Micky Duck,
My old Nosler no 1 Manual (1976) details the options of neck sizing, partial sizing and full length sizing in some detail so I won't repeat it. Neck sizing works well with light loads and partial sizing can work well with sub max loads with the more tapered cases. Full length sizing as defined by Nosler is where the case is returned to Factory dimensions for easy chambering. The problem lies in the tolerances for the dies and chambers. The gold standard for the set back of the case shoulder, when full length sizing, seems to be 0.05mm (0.002"). Only one of my sets of dies produces this result and only in one rifle. Generally the shoulder will be set back more and with some dies a lot more. This creates the excessive headspace that results in partial or total head separation as shown in the photos earlier in this thread. The fix is not to set the shoulder too much. To do this you need to be able to measure how much you are setting the shoulder back. Hornady sells a kit for this called a Headspace Comparator. This clamps onto the lower jaw of your callipers and lets you measure the case length to a point on the shoulder. Comparing the length of new, fired and resized cases can be a humbling experience but at least we will know how big the problem is. As I found setting the die down hard on the shell holder almost always over sizes the cases. You can carefully adjust the FL sizing die to achieve the right shoulder setback but my results with this have been variable. The deluxe solution ,with a deluxe price, is the purchase of a set of the Redding competition shell holders. These allow you to set the headspace of your cases to match your chamber with some precision.
For my loading I neck size for my old soldiers and light target loads in my .308. For full power loads for longer range target shooting I use the Redding Competition shell holders. I also check for the groove developing on the inside of the case with a bent wire paper clip at each loading.
Regards Grandpamac.