Neck Turning
Spud says..."There are two main instances for possibly needing to neck turn. One instance is when we would do a cleaning cut, this is where we aim to clean up 80% of the neck surface. This process will help even out the thick and thin parts in the wall thickness. When we are using bushing dies to control our neck tension, this type of neck turning will aid a more uniform neck tension and grip on the projectile. The second instance would be for taking the neck thickness down to a desired thinner wall thickness, for use in so called tight neck chamber guns"
As said above neck turning can be used for two separate scenarios. Most brands will have their own dedicated parts to their kits and its best practice to not mix match these if possible.
Neck turning will work best when you are using a bushing style sizing die. Wilson, Redding, RCBS, Hornady and Forster all make this style of die. It is worth remembering when consirdering your bushings for these dies, that you will want a smaller size after turning.
Always size after neck turning!.