I agfree with Colorado4QWheel. I are loading on my 550 because 1994 and that features a number of thousand CCI primers. I have not had a challenge with them not likely in easy. I've talked With all the Dillon people today repeatedly, but by no means about primer difficulties, considering https://federalprimers21037171.blogofoto.com/63115106/about-federal-large-rifle-benchrest-primers