My SRPs would seat just above flush no matter how hard I pressed with a Dillon 550. I also have a Redding
I was using my Dillon 550 to seat small rifle CCIs in Alpha 6.5 creedmoors. Always above flush, even after reaming the pockets. I also have a Redding T-7, but used the Dillon because it was faster and easier. I then tried the Redding and bingo, flush or below. My conclusion is that the shell plate in the Dillon was the problem. Just that thousands of an inch. However, after a few firings the Alpha Brass needed to be reamed or would still be above flush even using the Redding. Reaming done with a Hornady case prep drill. That is also a whole new issue, if you ream too much the primers fall out, if not enough the above flush problems rears its ugly head. Just have to use sight and feel. Bottom line is I wish I had not bought the Alpha Brass. Also never had the problem with large rifle primers even using the Dillon.