I had an interesting problem with some 5.56 brass when I started to trim the cases. My press is an RCBS and the cases all slid into the shell holder with no issue. However, my trimmer is a Hornady as is the holder that I use with it. Out of 100 mil. surplus cases about a dozen would not slide into the Hornady shell holder. Most went in without a problem and a few fit with some resistance. I reload 5 other calibers and have yet to have this problem,but this is my fist go round with military cases so that has me wondering if it's the cases that are inconsistent. I guess for now I'll go buy another shell holder and see if the problem cases slide in.