Reloading die dimensions are up to the maker. RCBS tech John Thor told me their designs are based on the SAAMI chamber minimum -0.003", ±0.002", except necks are even narrower to allow for the SAMMI neck brass minimum thickness (an indirect number you have to calculate as the minimum finished cartridge neck diameter less their maximum bullet diameter and the result divided by two) to still be resized. But that's RCBS's choice. I don't know what the others are using. If the ±0.002" is common in the industry, it explains why some people think one brand is tighter than another, when they may only have happened to get copies that were on opposite ends of the tolerance range.
I don't know what Redding uses. They do very nice machining so their dies are among the best looking. Their Competition Seating Die and their Profile Crimp Die and some of the newer sleeved sizing dies are slightly different than other and, IME, better than others I've used. But inexpensive doesn't always mean bad. The Lee Collet Die is great and their standard sizing dies still are, I believe, the only ones in the industry that are honed to final dimensions, a method that should keep them perfectly round in cross-section. The Redding Instant Indicator makes some measurements others aren't bothering with, like allowing you to measure shoulder-to-bullet ogive distance directly, which gives you the dimension that actually determines the final bullet jump to the throat of a rimless bottleneck cartridge chamber. There is a workaround you can do with a case and a bullet comparator, but it takes two steps instead of getting it in one.
As to turning necks before resizing, that used to be pretty difficult to do but now, if you go to 21st Century Reloading you can buy mandrels in half-thousandth diameter increments and put together a set that will let you find the right slip-fit for your as-fired cases if you prefer to turn those before resizing, as long as the mouths aren't dented. It's not the usual thing to do because of those dents, but it has the advantage that if do it before cleaning the cases, you get some lubrication effect from the carbon deposits in the neck. I've turned new cases and SS pin-tumbled cases and they tend to grab the mandrel and require inside neck lube to stop the brass from galling and building up on the mandrel.
Incidentally,
21st Century also offers nitrided mandrels as an alternative to investing in carbide mandrels. Unfortunately, they are in the middle of a website upgrade, so clicking on a lot of their products for more information just takes you to the same page at the new URL.
