If you want a specific neck diameter, you can get a neck bushing die, like a Redding Type S FL die. I use these for most of my match ammo. You could also take out the expander ball in the sizing die, and try it. The neck will be much tighter and you will need a good inside neck debur so the bullet doesn't catch or scratch on the case wall. Try this first. It could also increase the pressure of the round since there is more neck tension on the bullet. So, if you are running a max load already, test the load again before you load up a bunch of them to make sure it's not too hot of a load.

There is no adjustment for the neck, the sizing ball will size the neck the same everytime, the thing that pops the primer out is a decapper. A die that uses different neck bushings will allow u to change the neck tension. But for the most part all bullet diameters are the same for the caliber. What i do is push the bullet tip on something hard and see if i can manually push it in, if i cant then niether can the feed ramp.

Measure your expander ball and see if you have the proper interference fit.
Normal interference fit is about -0.002"
Take a 0.308 cal for example.
The expander ball will measure 0.308" ,minus interference (0.002")= 0.306"

You can polish the expander ball down to increase bullet tension. Use a electric drill and oil wet 1200 grit silicon carbide paper.
Careful how much you take off because you can cause high pressure if you increase interference to much.

Same can be done with a Lee Collet die. Or Lee will make you a mandrel to your spec.


Neck bushing dies are the easy way but they depend on the thickness of the brass neck wall. Thickness can vary with #shooting and different manufactures of brass. The neck sizing dies re-sized the OD. The OD will be uniform, But the ID of neck can vary because of wall thickness. Thus Giving you various interference & tensions. OD Thickness trimming will help alleviate some of variations. NSD also don't work hardens brass as much as conventional dies.

incredible information here. thanks for the insight. some of this gets a bit intimidating but the end product is really high quality.