I'd like to work up a load for my M77 tang safety 7x57 and have a mix of Sellier & Bellot and Federal brass. The problem I'm having is that the S&B brass will not fit in the #2 Lee shell holder like the Federal, the rim is too wide. I've got a couple of other shell holders that the rim will fit in but neither hold the brass tight, there is a lot of end play. I don't want to start loading a bunch of rounds only to find that the headspace is wrong, or pull of rims as I'm pulling them out of the dies. Any suggestions?