Let me see if I can explain this so some of you can help me. I am loading 308 using Sierra 175 HPBT bullets and resized brass of different headstamps. While seating the bullets I noticed there was a different feeling on the bottom of the stroke. The first 3 bullets I seated it was a firm sold contact at the bottom of the stroke but on the next two it was a springy feeling. At first I thought it was perhaps something I had done wrong during the resizing, so I resized them again but to no avail. It did not matter who the manufacturer of the case was. Also the "springy" ones were an average of .010 longer than the other three. Now these cases are on the 4th firing and I will discard after this. Has anyone else encountered this and if so can you shed some light on what it may be.