I know this post would be universal to about any caliber but I am going to specifically say 6br because that's what I load the most. The reasoning for the post is I have been waiting multiple videos of well known and very successful shooter from BSWN and their sizing techniques.
First off I want to say I'm still relatively new in the shooting community and have been mentored into using a body die to bump the shoulders back and to neck size. So far the results have been fantastic (for me). But I was kind of shocked when I heard all of these interviews saying they only FL size, they never neck size. So my question is why may that be? And what have you all found success with. Also not for my example these cases only have 3 firings on them.
Just got back from the range. I shot 25 rounds without any sizing. Fired cases, primed, powder, bullet. Nice groups. I was firing 6BRX cases after the first fire forming. Never did this before. Been reloading since 1968. As long as a fired case can be chambered easily it should be a perfect fit to your chamber and not a general purpose die. No control over neck tension. If you go to the Redding website they say something about the standard non-bushing dies may size a neck 6-8 thou to much. I know my non bushing die makes the necks way to small. I will continue sizing with my bushing die to control neck diameter. I was shocked a month ago shooting my favorite load in a 6BR. I thought I would try different COAL because of barrel erosion. Tried 3 COAL couldn't believe the difference in group size.