fired case shorter than new

I would size it to fit the chamber. Then keep a close eye on it for the next couple of firings. Are the Copper Creek rounds hard to seat in the chamber (heavy bolt closing)? What are you measuring your shoulders with?

Size a fired case with the die slightly (1/2 turn+) off the shell holder (well-lubed)
That should cause the case to grow/shoulder to move forward

Try to chamber the case -- use minimal force -- a see if there is any resistance.
If no resistance, measure case headspace dimension with your comparator and use this as baseline for now

Try another case, same thing. See if it chambers/measure case headspace. If longer baseline #2
Keep trying to get a case that wont chamber (or you get "feel") if you can. When you do, set the sizing die down graaaadually until it juuuust chambers. That headspace dimension is absolute baseline. Size to that dimension -0.002" forevermore.

If no case is too long/won't close, take the longest that will close for baseline and size to that dimension.

If it will still chamber, neck size only and shoot it again see what your measurements are then. Your chamber may be wide enough the the outward expansion was enough to allow the case length to be shorter after firing.

syhunt said:

@Allen One1 would you say my chamber is the fired size? I know that sounds like a dumb question but typically a shoulder will be pushed out to fit the chamber after firing..

Copper Creek rounds are not hard to chamber, everything chambers smooth as butter in my opinion. No evidence of pressure/ejector marks/primers/neck splits. Bolt isn't hard to open. In my limited experience I'd be leaning towards a headspace issue? If that was the problem I should see/feel that loaded round being hard to close on and would show some pressure signs.

Shoulders are being measured with the Hornady headspace comparator and my micrometer. Of the 60 fired cases I measured 15-20 at random and all are very consistent, within half a thousandth. Of the remaining 20 loaded rounds, all are very consistent, also within half a thousandth.

I have another box from them using Lapua brass, shot a few the other day so I'll take some measurements off that brass when I get home.

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I think the newly fired rounds are now fire formed to you chamber. You are probably pushing the shoulder back slightly as you are closing the bolt a crush fit so to speak. Of course I could be all wrong.

Scrupplez said:

If it will still chamber, neck size only and shoot it again see what your measurements are then. Your chamber may be wide enough the the outward expansion was enough to allow the case length to be shorter after firing.

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This is what I would do. FWIW custom die makers was a case that has been fired in the particular chamber at least 3 times to be fully fire formed.

If you continuously size smaller than the chamber and subsequently blowout the case, I would expect growth in brass and resulting reduction in its life.

If my case shortened from the shoulder to the case head when fired I would stop loading reduced loads.

I measure before and again after because I want to know what effect the chamber had on the case when fired. And then there are factors; because I have so many reloaders that do not agree with me I use my own list of factors.

F. Guffey

If the other brass stretched and these didn't I would suspect a larger case volume, resulting in lower pressure. Setup and measure what the case volumes are between mfg. Not sure I would set the sizing die for them if your going to shoot the other brass too. I would setup the sizing die for the Lapua brass and let the others fall where they lay.

I would size them all ( just a few of each brand) to a shoulder dimension of 1.595, load and shoot them again then remeasure the shoulder. Might even try 1.596 and see if they chamber nicely. That will get you just off the fired case length of both brands of brass after they are fired you will be able to see if they are getting closer together. This could get you to a final chamber dimension.

syhunt said:

Long story short, how would you set up a sizing die to size a fired case that's shoulder was set back 0.0025" from new after the first firing?

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My full length sizing dies are designed to return a case to minimum length from the shoulder to the case head; my shell holders have a deck height of .125".
If your cases shortened .0025" from the shoulder to the case head your cases are .0025" shorter than a minimum length/full length sized case. I form/size cases for short chamber, to accomplish this most reloaders would grind the die and or shell holder, some reloaders could grind both. If I was sizing cases for short chambers I would place a feeler gage between the deck of the shell holder and case head; I would do the same thing if I choose to increase the ability of the press to overcome the cases ability to resist sizing.

I have never fired a case that got shorter from the shoulder to the case head. By design all of my cases have gotten shorter from the end of the neck to the case head when fired ( and then there is the exception, I do not want to waste anyone's time so I will stick to the "never fired a case that got shorter)

'Unless the round was a reduced load' I have driven cases into chambers with a drift that fit the case head and small hammer. The driving of the case into the chamber would have a greater effect than the bolt slamming the case into the chamber on semi-autos,

Sequence of events: reloaders claim the firing pin shortens the case from the shoulder to the case head .005", back to loads that are reduced. I accept the case expands and locks to the chamber when fired, if the firing pin drives the case forward and shortens the case .005" + .005 clearance the case head will be .010" from the bolt face when the pressure gets serious.

I could ask, "what does that mean?" to save time I will tell you the case has no choice but to stretch .010" between the case head and the case body. For those that could put a little thought into it I believe they could come up with another factor in the sequence of events.

F. Guffey