I would like to try to remove the expander ball to see if it improves accuracy. Do I need to change the size of neck size bushing?

If you're using a neck size bushing such as Reddings you should have already done the math to see what size bushing you need??

Have you tried to mic the OD of the case necks to see how much you are reducing them? It should be a simple matter of mic'ing the OD and the case neck wall thickness to find the inner dimension. Do this after firing and then after sizing for a comparison. Normally you don't need the dimension after firing but it's an indicator of chamber wall dimensions and neck turing "may" be in order if only to true up the neck wall thickness.

thank you, but i know what size bushing to use with the expander ball. What I need to know is if the demention changes without the use of a expander ball. Your right, I need to get out the mic and check it myself.

Depending on your bushing, yes your dimension will change because the expander ball will not be doing what it is designed to do. In addition to puching out the primer it straightens out the neck walls and expands it to accept the bullet. I've sized cases for my .222Rem this way but found I had to use a VLD chamfer tool to be able to seat the bullets without collapsing the necks. The one drawback is I have to deprime the cases with a universal deprimer.

You should be able to size cases both ways and mic the ID of them to see the difference. I'm not sure how it will increase your accuracy but at the very least it will provide you with more neck tension. Lower deviations in velocity can also be attained by crimping but they don't always equate to increased accuracy.

If you bushings are set up to give you a .003 neck tension then you do not need the expander. All of my dies are set this way and it works really well.

high,

Unless you neck turn the cases will have a different brass thickness as you measure 360 degrees around the mouth. When you resize the case, whether neck size or full length, those irregularities are pushed to the inside of the mouth. The sizing button or expander ball pushes the irregularities back to the outside.

The size of your neck bushing will not change. But unless you have a custom tight-neck chamber, I think you're best to stay with the sizing button.

Just use a bushing that is .003 smaller than the neck diameter of a loaded round. Be sure your cases are deburred. If your bullet base has a sharp edge use extra care to seat the bullet without crumpling the edge. If your bullet has a boat tail it will seat normally.