Nonsensical Headspace Measurements on 223rem cases...??

[P2000]

Good call on the expander ball as a cause. I like that theory. What I mentioned only can only happen by a 1-2 thousanth or so until you can't even chamber the round.

Lots of us don't use an expander ball. I use a Forster full length resizing die with the expander removed. Then run a Lyman M die with some imperial dry neck lube but not all the way to the step. This opens the neck by 1 thousanth.

Another issue with your prepped cases is there is way too much variance in headspace. I measure headspace like you with the Hornady tool and calipers. My brass is very consistent, with headspace variations of 1 thousanth or less.

Try a test, grab 10 unprepped cases. Remove your expander ball and size them then measure them and see if they are consistent...if they are consistent you know the expander ball is causing problems.

Another thing to check is measure the same case 5 times. Do you get the same measurement? If not that is a problem.

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[darr3239]

With Dillons the powder die flairs the neck for placing the bullet, so I'm wondering if you need the expander ball at all after it's been sized once.

Don't know why I have thought of this before, since I've had some issues with loose neck tension on some calibers.

[markm]

Mark, what neck sizing die do you use?

I think it's just an RCBS .223 neck expander die. Every time I've forgotten the exact die, the subject comes back up.

With Dillons the powder die flairs the neck for placing the bullet, so I'm wondering if you need the expander ball at all after it's been sized once.

Don't know why I have thought of this before, since I've had some issues with loose neck tension on some calibers.

My Dillon flares on pistol only. On .223, I was getting jacket shavings without the expander die.

[markm]

Good call on the expander ball as a cause. I like that theory.

Most all in one sizing dies work by squeezing the neck down to an undersized shape... then they rip the ball back out to open it back up on the upstroke. This causes stretch, runout, excessive working of the neck, etc. It's all bad.

I don't think I'd use an expander ball even if all my ammo was fmj blaster.

[darr3239]

My Dillon flares on pistol only. On .223, I was getting jacket shavings without the expander die.

I knew there was a reason!

[P2000]

Most all in one sizing dies work by squeezing the neck down to an undersized shape... then they rip the ball back out to open it back up on the upstroke. This causes stretch, runout, excessive working of the neck, etc. It's all bad.

I don't think I'd use an expander ball even if all my ammo was fmj blaster.

Yup I can confirm the expander ball hurts concentricity. I went all OCD with an accuracy one concentricity gauge, and resizing without the ball, then with the Lyman M was better.

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[markm]

I went all OCD with an accuracy one concentricity gauge

Same here. I try not to live by every measurement possible... but the expander ball was worth the time to study.

[twadsw01]

Thanks guys. I will try to take some measurements as soon as possible, using my old Lee turret that I still have set up for this.

Side bar question: I use a Hornady FL sizing die and Lee seater an me crimp dies; anyone know if these are problematic in a Dillon progressive?

[bigedp51]

If you polish the expander and lube the inside of the case neck your expander will do no harm.

Below a close up photo of a new RCBS expander, polish it smooth or buy a carbide expander.



A case "grows" when full length resized and squeezes the case shoulder upward.



And variations in shoulder location are caused by brass spring back after firing and sizing due to brass hardness and annealing.

If you want more uniform shoulder locations then pause for 3 to 4 seconds at the top of the ram stroke. This pausing reduces brass spring back and more case uniformity.

I use a home made case lube of lanolin and alcohol and spray the cases inside a large zip lock bag. I then close the zip lock bag and squeeze and spread the lube and this puts enough lube inside the case neck.

Don't be a Ewok and not lube your case necks.

[twadsw01]

Okay. Will confirm that shell plate is making contact with the die. I would think - correct me if I'm wrong - that necessitates that the shoulder is indeed being pushed back, i.e., being set back the max possible amount.

If it is indeed pushing the shoulder back and being sized the max amount possible, then it would be most likely that the expander ball is increasing the headspace dimensions by stretching the neck on the way out, correct?

I'm using a Lee FCD for the crimping step, which I didn't even think touched the shoulder. So, is it more likely that the loaded rounds have shorter headspace due to being pushed back during the bullet seating step?