Once-fired cartridge headspace variation?

Y

YM13

Inactive
Hello all, first post here and first venture into the reloading world. I am experiencing a peculiar issue, to me it seems at least:

I have some once-fired 270Win brass from of A manufacturer out of my rifle. I have some once-fired brass from B manufacturer from my rifle as well, and C, and some purchased brass that was never fired. When trying to set up my die to resize just .001 below the fired cartridge size, measured using Hornady caliper attachment, I noticed the various cartridges from the different manufacturers show fairly significant variation in expansion.

My understanding is that the fired cartridge comes close or closer to a “cast” of the chamber. Probably this varies based on charge and thickness of the case itself. But, from the CoreLok cartridges, my fired measurements are not much over from the factory loaded and unfired ones.

I can post my measurements later so you guys can get an idea of the variation but wanted to get some preliminary thoughts about this. I appreciate the help!
 
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Just set the sizer die to contact the shell holder plus 1/8 turn and size the brass. Especially with the "purchased brass", you need to fully resize the cases to ensure they fit your rifle's chamber. Sizing has nothing to do with the cases' fired dimensions-at least not until you get into some extremely technical handloading. Forget all that hokus-pokus and load some cartridges that fit and fire in your rifle.
 
I have some once-fired 270Win brass from of A manufacturer out of my rifle.
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Start over, measure before and again after. and then the case does not have head space, the case has a length that is measured from the round hole datum of .375" to the case head. Try to think of your measurements as being made with a comparator.

If you want to measure the length of the case from the datum to the case head purchase a Wilson case gage. The Wilson case gage is a datum based tool. For years and years Wilson has suggested the reloader use a straight edge, for years I have suggested reloaders use a straight edge and with a feeler gage for accuracy; most reloaders use the Wilson case gage as a drop-in gage meaning they use their thumb nail for measurements.

I would not suggest you jump into reloading in a dead run. I understand reloaders talk in short choppy sentences like "I bump' or "I move the shoulder back .002"; it is not so much the .002" I doubt but no one can tell me how they move the shoulder back. I have tried and found moving the shoulder back is impossible: SO! I would suggest you avoid repeating everything you hear on a reloading forum. SAAMI says the case does not have head space.

F. Guffey
 
Thanks for the quick reply. I will do that in the meantime. I’m just trying to understand the variations and what is happening to show them. I have the tendency to go overboard with everything I do so it bothers me when I come across anything I don’t understand in the process, especially one so potentially technical as reloading.

The issue stemmed from obtaining information from various sources to size or adjust the die to minimize overworking of the brass so that the neck is .001 or so from what the fired dimension is. Thus my confusion when I ran into all sorts of variations in my fired brass.

Thanks!
 
Yes, different brass will give you different measurements.
I do get some variation in measurements even after firing them several times. Especially if you are bumping the shoulder .001: in my experience all the fired cases headspaces will not be exactly the same to within .001".
I have also read that once fired brass won't be fully fire-formed to your chamber.

Measure a few cases. Unscrew your sizing die a full turn, and then start screwing it in until you get .001" shoulder bump. As you try each case, make sure the case is lubricated every time. When you get .001" shoulder bump, then confirm the setting by doing a few more cases to make sure they are all coming out the same. When you are getting them all the same or very close to all the same; with a case in the shell holder, run the case fully into the die and then tighten the lock ring with the case fully in the die (this will help keep everything square). And you are good to go.

If I change brass, I do this all over again because of variations in the different brand or different batch of brass. All brass is not exactly the same. Different thicknesses, different elasticity (spring back)...............

Do keep your brass sorted by headstamp. Don't mix different brands of brass together when you are loading if you want to get the best possible results. Also keep a given "batch" of brass together throughout it's life. In other words, if you buy a box of factory ammo and fire it, keep it together for it's life so that you know how many times it has been fired and you should get fairly close measurements on all of it since it is probably all from the same lot number and all of that.

This is the reason I quit shooting just random brass in my precision rifles. I quit using range brass and all that. I bought GOOD brass and started from there. You get FAR less variation from case to case if all the brass is of the same vintage, the same brand, the same lot..................

I try to produce the best ammo I possibly can. I am not interested in just stuffing powder and bullets into a case and having something that goes bang. You are doing it right and taking careful measurements and trying to achieve consistent, repeatable results.
 
The issue stemmed from obtaining information from various sources to size or adjust the die to minimize overworking of the brass so that the neck is .001 or so from what the fired dimension is. Thus my confusion when I ran into all sorts of variations in my fired brass.
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YM13. I understand, I do not know how some reloaders ever get a case sized with all of their variations and jump back/snap back. And then they go to SAAMI with all of their +/- tolerance.

If you have three different cases with 3 different case lengths I suggest you settle on one manufacture at a time. I do not mix head stamps, I do measure the length of the case from the shoulder to the case head before firing, I want to know what effect the chamber has on the case when fired. There is a very boring conversation that covers soft brass. It normally starts with "I just hate that FC brass because the case heads are so soft and the primer pockets get loose in in two firings. If the primer pocket expanded the flash hole increased in diameter and the case head expanded and the case head shortened from the cup above the web to the case head. And that is not all.

F. Guffey
 
Glad to hear that I should expect some variations between case manufacturers. I figured that it should be something normal. I appreciate the input. So far I am keeping them all separate and will determine which give me best accuracy.

The rifle will be implemented mainly for hunting so I cannot help but feel like I am going way overboard; however I also cannot help but to attempt to achieve the highest precision I can. I either case I feel it’s good practice and definitely a learning experience.
 
Just set the sizer die to contact the shell holder plus 1/8 turn and size the brass.
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Sorry Mobuck but I have to disagree .

YM13 , you can try that with one of the cases then compare that case size to your fire formed cases . If the sized case is more then .005 shorter don't size the cases with the die set up that way . There is no need to size your cases down more then .003 from fire formed . Especially if you have the tools to measure the case from head to datum point . If I set up my 308 die as suggested above . My cases come out .009 shorter then my fire formed cases .After 3 loading I got these case head separations

G9JFNo.jpg


If you are sizing your cases down more then .004 you will be significantly reducing case life . Just slowly back the die off until you are sizing about .003 from fire formed and you should be GTG . I would also double check from time to time that your cases are being consistently sized to that measurement .



Keep in mind that the Hornady head space gauge I believe you are using is not a gauge per-say but rather a comparator . It is designed to compare one with the other and is not designed to give you the actual true measurement . I use one and it "measures" a 308 GO gauge .009 shorter then it really is . This is about the average these tools are off from true measurements . They are designed to compare one case to another only .
 
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The following is based on the assumption that your once fired brass was shot IN YOUR RIFLE. If they were not fired in your rifle resize enough that they will chamber and use a starting load to fire form, then use the following instructions.

This is how I set up my sizing die for bottleneck cartridges.

1. Take a once fired factory round and blacken the neck and shoulders with a Magic Marker or Sharpee pen. Some people like to smoke the neck and shoulder, but I find the Magic Marker/Sharpee pen a bit better.

2. Carefully lubricate the case.

3. Loosen the lock ring on the sizing die and back off about two turns from when the die is set to touch the shell holder.

4. Size the case. Note where the marks are on the case and turn the die down about a half a turn and size again. Turn down some more, and resize again. What you are looking for is the marks on the blackening just touching the shoulder.

5. Clean the lube from the case and try it in the rifle. It may chamber just a bit on the snug side. If so, turn the die down ever so slightly, lube and size again. Wipe off the lube and try in the rifle. If it slides in as easily as a factory round, you should be good to go. If not, usually one more very slight adjustment should fix the problem.

6. Tighten the locking ring for the die and you're done. You have just set your sizing die up for a custom fit to your specific rifle, rather than a generic one size fits all guns.

Paul B.
 
Great info thanks!!

I may be mistaken but when I checked my fired rounds chamber back into the rifle just fine. What’s up with that? Is that not supposed to happen?
 
you need to fully resize the cases to ensure they fit your rifle's chamber.
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Mobuck, when I fire a case in one of my chambers and if what reloaders claim is true about case jump back, snap back and recovery the case should fit the chamber when it is extracted. If reloading was not so complicated and if it was easy for r4eloaders to keep up with the details they could remember it should be possible to neck size the case only for chambering.

And then there is that other part that complicates life for the reloader; In the perfect world the sizing die is designed to size a case to minimum length 9that is the same as full length sizing), but reloaders will not spend the time to master the art of sizing a case. In the perfect world my 30/06 sizing die is .005" shorter than a go-gage length chamber from the shoulder of the die to the deck of the shell holder. When full length sizing a case to minimum length I should have .005" case head protrusion from the die. If I wonder if the press and case sized the case I should have no gap between the bottom of the die and top of the shell holder. And then there is the magic .002" clearance, I have asked; "Where did that come from?" I never get an answer but I do read about reloaders bumping the shoulder back .002", Yeaw, we have a lot of bumpers out here.

F. Guffey
 
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They should chamber but normally they will have a little resistance closing the bolt compared to how the factory rounds did .
 
I may be mistaken but when I checked my fired rounds chamber back into the rifle just fine. What’s up with that? Is that not supposed to happen?
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What is with that? That is the way it is supposed to be. There is such a thing as a neck sizing die, I have neck sizing dies, I do not use them but I have them just in case. And it is possible to neck size with a full length sizing die. This is the reason I believe it is a bad habit for a reloader to jump into reloading in a dead run. And then there are the hacks, they want to take short cuts, they do not want to learn required information when starting and they do not want the required information to finish. They just want to flat rate.

F. Guffey
 
They should chamber but normally they will have a little resistance closing the bolt compared to how the factory rounds did .
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One more time: had he measured before and again after firing he would know the difference or as I always say 'the reloader would know what effect the chamber had on the case when fired'.

F. Guffey
 
Gotcha it makes sense to me that it should chamber since it would be confirming to the chamber but it seemed from the discussion that that should not be the case.

I’ve read up on reloading for about a year off and on before jumping into it and deciding to get involved with it. As you can tell I want to account for and understand all of the variations and why I may be experiencing them, ultimately in hopes of pulling out some savings and mostly greater accuracy.

I appreciate you guys helping me out!
 
Let me go back and post the “comparative measurements” I’m getting so you guys get a better understanding of the variations. What confused me is how cartridges could have such a wide variation despite being fired in the same chamber between manufacturers. I’ll have to go back and see if they are all constant at least within the same stampings. I don’t remember now as I was measuring just to see what they all looked like.
 
Oh very important , I forgot to tell you to remove primers before measuring your fire formed cases . You don't want any interference from the spent primers throwing off your measurements . Also give the cases a slight spin/turn while measuring in order to square them up in the calipers .

Not sure if you use this but I like to use the anvil base that attaches to the opposite arm of the calipers . It makes it easier to square the cases up rather then having them sit on the edge of the caliper it self .
https://www.midwayusa.com/product/584824/hornady-lock-n-load-bullet-comparator-anvil-base-kit

Also don't use the wheel on the calipers to close them because that can cause them to flex . Rather pinch the jaws closed with your fingers . ( ignore the red circle , the picture was taken a long time ago for a different subject )

XWsE7f.jpg
 
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I would not allow it to drive me to the curb, I have loaded 12 different loads for a 270 with 10 rounds in each group, The cases included new, once fired, military, commercial cases. Each group got a different case head stamp, I built the rifle and cut the chamber.

At the range I I did not have a flyer and I did not have groups tha topened up, all of this was about finding what the rifle liked. I loaded another 1\120 rounds with 12 different head stamps, bullets etc. and then delivered the rifle with the understanding he needed to determine 'what the rifle liked'. Again, none of the groups opened up and there were no flyers.

F. Guffey
 
Each mfg has a different metal mix as well as annealing.

As it does drop back a bit after firing, a difference is not at all surprising.

Either deal each mfg as a one off and set the die or pick the worst and set it.

I would try the first and see if you can get them to go in ok for each mfg.
 
"If I set up my 308 die as suggested above . My cases come out .009 shorter then my fire formed cases .After 3 loading I got these case head separations"

I used to have a .308 like that. Setting the barrel back a thread and a new chamber FIXED IT.
 
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