Are you talking about neck turning? Trimming brass does not affect neck wall thickness
I'm pretty sure the OP means "neck turning", i.e. removing excess brass from the neck wall in order to get "consistency" in neck thickness,... and that's really the word-of-the-day: "CONSISTENCY". There really isn't a prefered wall thickness. A lot of variables can come into play, (brass thickness, brass consistency, chamber dimensions, desired neck tension, etc.) and depending on who you talk to and your desire to fiddle with it, you can go hog-wild tweaking neck thickness and neck-sizing to get the perfect combination of neck-tension, and wall-thickness for your load and chamber,... at least in your opinion.
Again, reloading quality ammo is all about consistency and getting uniform wall-thickness from turning the necks is another step you can take to achieve it. What exactly does neck-turning achieve? Well, it primarily allows for consistent neck-tension on the bullet, thereby allowing for a consistent release of the bullet, thereby potentially tightening up the SD of your shots. I guess a case can be made for it also improving the concentricity of the bullet when seated, thereby making the engagement of the bullet into the lands more consistent, but measuring that is all but impossible (impractical).
I've turned my fair share of necks over the years and while it's not difficult to do, it's necessity for accuracy, at least in my practice, is a variable I'll only consider when certain criteria are met. In other words, will the investment in time and effort, not to mention money, be repaid in enough added accuracy given the intended purpose of the rifle and components I intend to use.
For me personally, I'll only turn necks if the rifle is intended for benchrest or F-class (long range shooting for group/score type accuracy), or if I have a barrel with a tighter chambering (only had that on one benchrest rifle) that will only chamber thin-necked cartridges. If the rifle is for shooting in the field, i.e. practical competitions with the occasional poke out past 1000-yards, just getting quality brass that is known to have consistent (enough) necks from the likes of Lapua or Norma is usually all that's necessary. If all I can get is crappy brass that is showing to have really inconsistent necks, I "might" consider turning them, but only after I've given the stock setup a thorough testing for accuracy. If they just aren't shooting the way I want them to, or I see occasional fliers that weren't caused by me, I "might" do it. Even then, I've found that neck-turning has more to do with my own peace of mind than on the accuracy it achieves, YMMV.
Ry
