Is there any reason here why one couldn't FL size the brass, then follow up with a run through the collet die? I would think that this would minimize run out on the FL sized cases throughout the case life regardless of neck thickness, and keep the neck tension under better control.
The only real problem I can think of would be that depending on the case and neck thickness, it might be hard to slip the collet die mandrel into the FL sized case.
This thread started the very same question.
I've been considering an initial test of this idea as soon as this weekend, but is also contingent on getting some bullets that are overdue in shipping.
I prepped 15 cases this morning using a basic RCBS FL die and the Lee Collet Neck Die. The FL sized cases fit in to the Collet die just fine.
The idea makes some sense, but if you read through a number of Bart's recent posts regarding FL sizing, which is darn interesting, it's easy to assume that neck sizing is irrelevant or unnecessary.
My feeling is that it's a matter of to what level of handloading precision are you striving for, or perhaps, there's more than one way to skin a cat.