Is the expander ball on the decapping stem of the neck die really necessary? Once the cartridge has been fired does the case neck open enough to enable the seating of a projectile when the case is reloaded?

Best Regards,

When you resize the neck, the die squeezes the neck down to where the neck is undersized. The expander ball then brings it back out to almost caliber diameter. If the neck was left too much undersized by the neck sizing, the pressure of the bullet being seated, might instead collapse the neck and shoulder area of the case as you press the bullet.

A once fired case, or should I say it's mouth, is often oversized after firing, and a new bullet often will slide inside the case with no tension or friction from the neck. This of course depends on the actual dimension of the chamber and how much it allows the case to expand.

Yes, it's very important. It makes the necks round before they hit the sizing die, if you didn't have it and a case was way out of round you would most likely get it stuck in the die.

no.... do the math on how much tension you want on your bullet. and buy the correct redding bushing for your bushing neck die made by them.

I have recently abandoned the expander ball. I've heard and noted that it will effect accuracy.

I have had no problems simply partial neck sizing my brass.

I remove the expander from some of my dies when resizing and use boattail bullets in the brass. Actually I`ve used flat base a time or two also and have yet to collapse a case. The expander will add to runout and cases FL sized without them show very little runout in my limited experiance.
Neck tension will be tighter then normal when you do this, and it can affect accuracy. In my 6.5x284 and 223 it works out for the better.

It depends. If, as explained above, the die truely squeezes down the neck to be way below the size you want for proper neck tension, the consequence of leaving out the expander ball is that you ask the bullet to perform the expansion job for you. This could well lead to damage to the heel of the bullet, and that is the worst place you can damage it in terms of accuracy.

On the other hand, the next die-brass combination may not size down the neck as much, and you might get away without the expander. Measure neck diameter of loaded round and neck diameter of sized (not expanded) round, if the difference is much above .005" you probably want to use your expander.

Alternatively, you buy a Forster sizer, and send it to Forster and have them modify the die ($10 + shipping) to size the neck to the diameter you want - all without the use of the pesky expander! Very low to non-existant run-out!

- mike

Thanks everyone for taking the trouble to reply. All the replies have given me "food for thought".

All the best!

I should have added in my original post that useing a sizer minus the expander will, as long as the chamber wasn`t crooked leave almost to no runout. Then with the expander screwed back in but left a 1/2 turn loose, or just snug on a rubber "O" ring, run the ball in the case mouth just enought to reopen it . This will reduce runout to as close to zero as you will get or equal to what you get with a Redding or RCBS bushing die.
The down side is time......you go through the "motions" twice,but you don`t need to keep 3-4 "bushings" on hand to allow you to use different brass of varying thickness. I figure it as a cheap way to achive runout free brass although neck tension is not as even as with bushing dies.

If you are trying to achieve "benchrest" standards w/ your reloads, then remove the expander ball b/c it does nothing to uniform the cases--as long as they will be shot in the same rifle.
You will need all of the special tools and gauges to be able to "measure" the differences in your loads. If you go this route, prepare yourself for some interesting/challenging//eyeopening/unknown results.

A friend of mine used a benchrest quality barrel with a tight chamber. He had to turn the case necks to the right diameter. Then when he shot the 22-250 it would not expand so much as to need to have the necks resized or the brass for a few rounds until the brass stretched and he would then use a body die. This system does not work with any of my factory rifles as they are all factory loose fitting chambers.

Hope I didn’t confuse you to much.