Thread: Full Length or Neck sizing. What is better and why?

Originally Posted by Pommy

The downside with bushing dies is that for best results - or even just for acceptable results (depending on your standards) - you need to neck turn brass.

Bushings can also lead to donut formation because they cannot size the base of the neck, meaning that material is able to accumulate.

I have also read that quite a few folk get quite a lot of runout with bushing dies. How much before it actually starts to matter? That probably depends on a lot of things. It's probably also not incurable.

Personally, I have had Redding bushing dies do weird stuff to brass fired from factory (i.e. generously sized) chambers. If they have to neck down the brass more than about 6 thou, the bushing leaves the top of the neck flared and the rest of the neck undersized, resulting in too much neck tension. I contacted Redding about this and it was a known thing:

"If we start to size down more the .006” or so from a fired case that exact thing happens. The chamfer that leads the oversized fired case mouth into the bushing is rather abrupt and steep. This can cause the brass to over shoot the bushing diameter and then come back out to fill it."

The Redding body die and Lee collet die combo suffers none of these issues.

Exactly the experience that two of us have had which led me to make custom FLS dies to suit machined necks. If the necks thin out over time and the custom die cannot reduce that last bit needed a custom collet die can be used successfully without the usual ridges being formed because the brass is now only being reduced approx 0.001" over the mandrel.......depending on your accuracy needs bushing dies will work, but not if you want top end performance at long range.....