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

[bigedp51]

Chambers and resizing dies vary in sized and your die is adjustable up and down for the correct amount of shoulder bump.

Example I have a standard Lee full length .223 die that reduces the case diameter more than my RCBS small base die. And this same lee die will push the shoulder back .009 more than my .223 GO gauge if it contacts the shell holder.

I do not have a progressive press so I assume when you say "shell plate" you have a progressive press. But it is my understanding a progressive press can cause more variations in shoulder location. Meaning if the case does not make hard contact with the shell holder it will not remove any flex in the press and variations in shoulder location.

I use Redding competition shell holders to control shoulder bump on my Rockchucker press to eliminate flex in the press.

Bottom line, press flex and using mixed brass will cause variations in shoulder location. So again, adjust the die for proper shoulder bump and try pausing at the top of the ram stroke. And remember if the die is adjusted too low and you bump the shoulder back too far this can cause shorter case life and case head separations.

Below a "FIRED" Lake City case from my AR15 and my sizing die is adjusted to push the shoulder back .003 from this measurement. For a semi-auto the thumb rule for shoulder setback is .003 to .006 and if needed you can average the amount of shoulder bump between these two points.

[twadsw01]

Thanks for the info.

Gotcha on the shortening too much thing; definitely want to not be overworking my brass if I can help it.

Correction: I've not loaded any on a progressive as of yet, but was only looking at measurements to begin with since I was about to start setting up my Dillon for reloading 223. Everything this far has been loaded on a Lee turret, and for confirming measurements in the course of investigating the conundrum I initially posted about, I will continue using the Lee press.

You're correct - I did use the wrong terminology. I should have said "shell holder" instead of shell plate.

Chambers and resizing dies vary in sized and your die is adjustable up and down for the correct amount of shoulder bump.

Example I have a standard Lee full length .223 die that reduces the case diameter more than my RCBS small base die. And this same lee die will push the shoulder back .009 more than my .223 GO gauge if it contacts the shell holder.

I do not have a progressive press so I assume when you say "shell plate" you have a progressive press. But it is my understanding a progressive press can cause more variations in shoulder location. Meaning if the case does not make hard contact with the shell holder it will not remove any flex in the press and variations in shoulder location.

I use Redding competition shell holders to control shoulder bump on my Rockchucker press to eliminate flex in the press.

Bottom line, press flex and using mixed brass will cause variations in shoulder location. So again, adjust the die for proper shoulder bump and try pausing at the top of the ram stroke. And remember if the die is adjusted too low and you bump the shoulder back too far this can cause shorter case life and case head separations.

[bigedp51]

Just remember if you are using range pickup brass or buying once fired brass the case headspace measurements "WILL" vary.

Also different brands of new brass will vary in headspace length due to brass spring back after firing. Just like the case will spring back larger after sizing, this is why pausing at the top of the ram stroke helps. This lets the case know who is the boss and stay put after sizing, meaning far less brass spring back.

[markm]

Gotcha on the shortening too much thing; definitely want to not be overworking my brass if I can help it.

Again... CASE GUAGE. It has a min/max. It's a no brainer. Factory ammo usually seats at the min. I set my die to size to average in the middle of the min/max. Over max and you'll get troubles going into battery.

[twadsw01]

The vast majority of what I have in my unprepped bin had most recently been fired in my rifle. There are, however, some occasional pickups that aren't from me.

Just remember if you are using range pickup brass or buying once fired brass the case headspace measurements "WILL" vary.

Also different brands of new brass will vary in headspace length due to brass spring back after firing. Just like the case will spring back larger after sizing, this is why pausing at the top of the ram stroke helps. This lets the case know who is the boss and stay put after sizing, meaning far less brass spring back.

[markm]

There are, however, some occasional pickups that aren't from me.

Range pick ups don't matter. It's all going through your sizing die anyway. Pappabear and I have scooped up many thousands of rounds of range brass. Every so often you can get a case separation, but that's an inconvenience, not a safety concern. I think I've had 5 in my entire .223 loading career.

I do toss out brass that requires an out of the ordinary amount of effort to resize.... assuming it's been fired out of an out of spec chamber/excessive head spaced gun.

[bigedp51]

Range pick ups don't matter. It's all going through your sizing die anyway. Pappabear and I have scooped up many thousands of rounds of range brass. Every so often you can get a case separation, but that's an inconvenience, not a safety concern. I think I've had 5 in my entire .223 loading career.

I do toss out brass that requires an out of the ordinary amount of effort to resize.... assuming it's been fired out of an out of spec chamber/excessive head spaced gun.

If I remember correctly markm you are using Dillon dies that are small base dies. Meaning with a standard die brass springback and brass fired in another chamber can matter. Normally a small base die will push the shoulder back .003 more than a standard die.

[twadsw01]

So, here is some additional data, which indicates that my initial measurements prompting this thread might have been erroneous in some way (maybe not zeroing out the mic, etc., etc.,?). I took twenty cases from totally unprepped through the reloading process, sans powder and primer. The purpose was to be able to see how individual cases were effected by each step in the process.

The same process as I normally employ for reloading was used, and I did not ensure the inside of the necks were lubricated (simply due to the fact that I wanted an apples-to-apples comparison with the cases I originally measured for this thread).

I will dump the raw numbers (screenshot form), and two box plots, showing length and headspace after each reloading step (where applicable - e.g., did/can not measure case length after a bullet has been seated).

In my opinion, nothing looks out-of-place here. Cases lengthen after sizing then the longer cases are indeed being trimmed while the shorter ones aren't touched by the trimmer - this is readily observed by the box plot, where it appears that simply the top of one box has been lopped off, leaving the bottom untouched. Also, unprepped cases starting with longer headspace get bumped by the sizing die, while shorter headspace cases do not, and none are being bumped back an undue amount, it seems (0.002" on average).

- Average case length comes out to 1.750", as desired.
- Average headspace is 1.462".
- Average case length growth from the sizing die is ~10/1000".
- As mentioned before, average shoulder setback is 2/1000".

There are still some high outliers in the headspace category, which could be explained by the spring back phenomenon, possibly.

Of note is that the one case that started with shorter headspace than where the sizing die was bumping all the shoulders back to - case 18, 1.461" unprepped headspace measurement - this case's headspace actually became longer in the sizing die, as expected because of the brass growing while being inserted in the die, but the shoulder never being setback by the die. Is this a concern? I.e., could this cause the head of the case to become unduly weakened due to the brass never being 'crunched' back down at the end of the stroke?

Does anything look strange, unexpected, concerning about any of this?

Also, thank you, everyone, for all of the input into this thread. I appreciate it.

[markm]

You are a glutten for punishment huh?

My sizing die set up is simply turning the die down until a 5 case average squeeze is in near the low shelf on the case gauge. Even with good case lube, not every piece springs back the same. So if 5 pieces look pretty good, I'm done.

[twadsw01]

I got access to the equipment and tools I got access to. Just wanted to get it done. However, case gauge wouldn't give me actual numbers, right?