Thanks fellas!

by CJM , Saturday, November 15, 2014, 22:39 (3601 days ago) @ Hoot

If the brass is shrinking in length, it's also either growing in diameter, or the neck is changing in angle to bring that case mouth back closer to the case head. Get a decent dial caliper or set of micrometers to measure both the unfired and fired cases and find where they are different. Measuring the case head diameter, the shoulder diameter, the shoulder length and the length from the case head to the case neck should tell you what is happening.
According to Ken Howells "Custom Cartridges" the 8x57 should have a case rim diameter of .473", a case head diameter of.4716", a case shoulder diameter of .431" that is 1.83" from the case head, a case neck diameter of .349 that starts 1.933" from the case head and a case length of 2.24". The shoulder angle should be 20 degrees, 48 minutes but that really isn't possible to accurately measure directly with the equipment any of us would have, even guys with full machinist setups.