Thread: Interesting Article on measuring Case Head Expansion

Here is the link

http://www.shootingsoftware.com/ftp/...%2019%2004.pdf

Most of it was over my head, hopefully some of the engineers on here can understand it.

He is basically saying that if you stick to the books and follow safe reloading practices you wont have a problem. I also think he is saying CHE and PRE are extinct due to properties of different brass.

I dont worry about it as much as I used to. As long as my primers are snug and I can chamber a neck sized round for 5-6 loads I know I am sweet. I have measured the CHE on cases that have been fired 10 times and they are close to .0007 but will still size and chamber and hold a snug primer easily. 10 loads is enough for me and they get binned anyway.
He also points out if I am not mistaken, that strain gauges are a waste of time.

Re Strain gauges, I think he actually shows they are good

This part from the article shows some sort of statistical analysis where the smaller the number the better. Also if you look at the website it is selling RSI Pressure Trace strain gauge system.
CHE method, 7,500
PRE method, 6,800
Copper crusher method, 1827
Commercial piezoelectric, 1366
PressureTrace™ strain gauge, 667

Originally Posted by stug

Re Strain gauges, I think he actually shows they are good

This part from the article shows some sort of statistical analysis where the smaller the number the better. Also if you look at the website it is selling RSI Pressure Trace strain gauge system.
CHE method, 7,500
PRE method, 6,800
Copper crusher method, 1827
Commercial piezoelectric, 1366
PressureTrace™ strain gauge, 667

Your right., I read to fast for my small brain sometimes.
I used to get hung up on CHE.
I reckon other things show before it is a concern.
I used to also be a bit of speed chaser but have learned chasing finite accuracy and consistency is cheaper. What's a few extra clicks on the turret when it requires turning anyway.
Good article all the same. Cheers for posting.

Thanks stug, interesting article. I have found, or incorrectly thought I had found (if this author is right !), CHE to be quite useful though. I first picked this up from Nick Harvey's description in his reloading books. This was on Winchester+P brass in the .257 and Remington brass in the .280. CHE correlated consistently enough with QuickLOAD predictions and a PressureTrace in both cases with expansion typically not measurable within the precision of my mic up to around 67k peak PSI and then would take off, usually to 0.01mm+ (>0.004") once the peak pressure was over 70k - same with both lots of brass. Just checking my notes and it seemed to be more consistent than this article is saying. Working up in 1 grain increments and maximums would always show one or more cases with significant expansion. Back off 2 grains to a regular load - somewhere in the 62-65k range - and never any measurable expansion, so CHE worked for me. Having repeatedly matched fired primer appearance, and particularly the onset of slight cratering (sloppy mauser pins) on the primer to the estimated pressure I'm comfortable just using these visual signs for load development now, but at the time CHE seemed just fine for IDing max loads.

If you got 0.01mm expansion that is 0.00039 of an inch
So less than half a thou not four thou of an inch

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Thanks... careless. Should just stick with metric, meant around half a thou. 0.004" would be problematic I imagine. You're clearly mathematically literate despite your claim! So yes, CHE work fine for me, but as with R93, no real need for it nowadays, with dialing capability on the scope and better accuracy preferred over going all-out to maximise a given point blank range. Still trying to offload my light-for-calibre Barnes-X stash now that I've gone the other way with VLDs.

Keep the barnes for sub 300 :thumbup:

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Greg Duley suggested the paper clip test. Been a valuable tool when buying pre fired brass i.e stops the lies as well as been a valuable safety test.

The yanks who dont kill by Drone also think about this issue.

what causes case head exspansion ?