Chan's bullets are flat base. Very accurate bullets, more so than my Bergers and Genco's, but about the same as BlackHole bullets. As for performance, Chan's have no equal. The other bullets are good, even great, but Nagel's are just so consistent.
I'm the opposite of Tim, I prefer flat base bullets. I find them easier to develop accurate loads for. I chamfer all of my case mouths and use a Forster Benchrest Seater die. I haven't had any problems with that combination yet.