I have learned a lesson from the school of "You should have paid attention". I am using a Sinclair bullet sorting stand with their comparator base to measure my new 130gr, 6.5 Hornady ELD-M's. I get near the end of sorting 400 bullets and notice that measurements are jumping way up. Can't be right lets check the 2 knobs, both are tight. The dial caliper is still zeroing. What's going on. Pick up the comparator, wipe off the base of it and the granite, no relief there. Grab a cotton swab and clean out the comparator with some acetone making sure not to leave any cotton inside and check. Yep that was it. Went back and checked the sorted bullets to find that they were off also. Back to the beginning. Just 400 more to do. Incidently the ELD-M's are remarkably uniform, at least from base to where the ogive is estimated by the base. I wish I could say the same for lot to lot consistency. This lot is 0.006 shorter from bullet base to ogive than my previous lot.