With another Redding Type S FL Bushing Die on order; I am starting on a project to compare different resizing methods vs concentricity. My intention is to measure neck concentricity on 10 case batches - 10 collet sized, 10 collet + body sized, 10 bushing sized w/ Redding FL bushing dies, and 10 conventionally FL sized with the Lee FL die. This will be done with my 4 calibers - 223, 243, 7mm-08, and 30-'06. It'll take me a month or two to get it all done. I'll publish the results, here. I started yesterday.
I sized 10 fired, 30-'06 cases, with the Lee FL die, then checked neck runout. I did the same thing, this morning with 10 .223 cases, also with a Lee FL die. Interestingly enough, all 20 cases neck runout measured under .001". That may not surprise some of you; I really didn't know what to expect. I'm just getting started, but, I'm starting to wonder if this is all a function on how small the neck is sized and then what occurs in the seating process.......