Larry Willis does not claim to resize "the belt" in any publication I have seen. He resizes the case "from the belt" forward
I never said he does….what he does claim is that due to the die not sizing the belt, which is impossible because it is solid brass, that this causes the bulge.
What causes the bulge is a chamber that doesn’t fully support the case head, thin brass and oversized chambers.
It has nothing to do with the belt.
Coned breech chambers in certain rifles cause this bulge, Norma brass is notorious for this as the web is actually below the front edge of the belt…section a case and see for yourself.
The collet die addresses the issue, but it does not change any of the above if the brass is being oversized. As I said, I have never had any of these issues.
I load for 257 Bee, 264WM, 270 Bee, 300WM, 300 Bee, 338WM, 340 Bee & 375 Bee. I also load for 458 Lott, but that is a different kettle of fish.
If you bump .002” and, end up with .001” head clearance due to spring back, then all should be good.
Even a rimless case that is sized too much will exhibit incipient case head separation.
I have had my fair share with this on my 6.5x55, it was a known problem with the brass at the time, similar to how people are having trouble with 280AI and PRC.