Okay, I'm not sure how to search for this. I've been searching and can't find an answer. I must be missing something.
I recenting picked up a used RCBS Luber Sizer. The sizer had a .357 RCBS sizer die in it, and I played around with it and got a feel for how the machine works. But I needed some other sizing dies, so I went shopping. I needed a .358 die. RCBS dies were not in stock, so I ordered the Lyman sizer die. And since I was on the Lyman page, I order several other sizes as well (all Lyman).
Today, I get my new dies. I'm all excited. Ready to size some bullets and seat gas checks. I start with the .358 die. I put the gas check on the bullet, size the bullet; the gas check is seated in the process. Wow! Nice looking bullet! When I place it on the table, I notice something. It's not sitting straight. Actually, it wobbles because the gas check base is rounded. I try another bullet. Same thing. Then I look at the end of the plunger in the Lyman sizer die. The end is concave. No wonder the bases are rounded. I check the RCBS plunger in the original die that came with my machine. It is flat, not concave on the end. Now I'm looking at the other Lyman dies, and all of those plungers are concave! So, I expect the GC's will also be rounded on the bullets I size using the Lyman sizing dies.
I did swap plungers between the RCBS and Lyman sizer die, and now all my CG bases are flat. But what about the other Lyman dies and GC's?
Am I being hypercritical of a rounded GC base? Would this be an issue in actual use? Do all plungers in the Lyman product have concave ends? The new RCBS?
What am I missing?