I just washed about 500 RP cases so this thread had me interested!! I have the MG 230 JHP but they seem to seat ok, and I thumped (technical term?) one on the bench but there was no setback and that was before the FCD bell removal. I then measured the bearing surface with the calipers and it showed .450 - strange, but then I mic'ed it and the very base of the bullet is .4510. Up a few thousands from the base and it's back to .4500 - I guess I was expecting the majority of the bearing surface to be .4510. Since the base of the bullet is deepest in the case I'd expect that to dictate setback.
Since the OP had Win and Fed HS exhibit good behavior, it's probably not the bullet size but it might be worth a quick check.
I did come across an article which I'll link here, and I'll quote the one section that had me interested in the sense it's a quick litmus test to see if your sizer or expander might be an issue.
http://www.massreloading.com/setback.html
"
Your dies are out of spec
This is an unlikely cause, but if you are using a set of dies for the first time, and your cartridges fail the bench test, it's worth spending a few minutes to check the dies (I've ended up with three sets that were out of spec in the last ten years). Run a case through the sizing die and measure the inside diameter. It should be no larger than 0.002" under the bullet diameter. In other words, if you're loading .45 ACP with a 0.451" diameter bullet, the inside diameter of the case should measure no larger than 0.449". Next, run a sized case through your expander die and measure the inside diameter. Again, the ID should be no larger than 0.002" under the bullet diameter. If the dies are out of spec, there's no easy way to fix them. Contact the manufacturer for a replacement. "
I tried this and my dies were at least .002 under. They're vanilla RCBS carbide, probably 20 years old.