Re: neck tension and increased pressure
Yeah, and then if you are dealing with something like a 220 Swift, for instance, you have to decide whether to toss the brass, inside ream, or outside turn the necks. (or whether it is worth it, at this point) You get a lot of brass flow in certain cartridges. So, you have to be careful about your over all length and the possibility that the necks are being crimped when chambered. There is also a possibility that you have developed a "donut" inside, if you have already worked the necks. Just to clarify, you mean .0010 total neck tension, not wall thickness?
What do your primers look like?