Has anybody had this happen before?

[quack1]

I made 100 25-20 cases out of new 32-20 brass. After 3 reload/fire cycles there are 24 of them that have developed irregular mouths, the picture shows some examples.
Some of the worst mouths are .025" difference in length. I noticed a few slight mouth irregularities after the first firing, but dismissed them to the brass getting fireformed to the chamber. The irregularities got progressively worse with the next two firings.
What I have done: The necks were annealed before forming to 25-20, and all were trimmed to minimum length. All were loaded with 10gr 4198 with Lyman #257283 and fired in a Savage 23. After 3 loadings all brass is still slightly less than trim length. I would expect this as the brass was new and would shorten slightly when fireformed with the first shot. I don't pull the brass over the expander button when sizing, I only use my self machined M die to expand the necks .002 smaller then the sized bullets. I don't crimp, just remove the slight bell. I don't have a tubing micrometer, but as far as I can tell with calipers, the mouths are pretty even in thickness all around.
I think I covered everything I have done to the brass, if there are any questions, ask.
The part I don't understand is that the low sections of the mouths have shrunk, rather then the rest of the mouth stretching. I've been loading and casting for over 50 years and never came across this before.
Anybody have any comments on what might be causing this? And better yet, how I might stop it. I'd hate to end up trashing the uneven brass.
199202

[Bzcraig]

Grumpa (vendor here) does a lot of brass forming so this should be in his wheel house, might want to shoot him a pm.

[tazman]

Just out of curiosity. Have you checked the orientation of the brass in the chamber?
I don't know if it would matter, but if one portion of the chamber is a bit different(diameter or angle) it might effect how the brass stretches or forms itself.
The low spots may be coming from the same side of the chamber if this is occurring.
Just speculating here. I have no proof to base this on.

[rond]

Is the shoulder moving forward? Headspace is a little long in my 23, I just touch the shoulder when resizing.

[Tom Myers]

Just a thought.

What method was used to anneal the brass?

Is it possible that one side of the cases were not as hot as the opposite side during the annealing process?

[blue32]

My 32-20 starts to do that after 8-10 firings. I always figured it was the relatively thin case mouth with expansion and resizing on the case. Maybe a 25-20 would put more pressure on it.

[Guesser]

My 32-20 revolvers do that with factory cases after several years of loading and shooting. I remember wondering if it would happen if I used jacketed bullets. I never tried them, just ignored the problem and went unloading and shooting cast. One thing that occurred to me was the powder charge. 3.0 gr. of B'eye kinda strings out the full length of the case unless you tip the gun up and the powder drops back over the primer so ignition is not a "string". I've been using Trail Boss for several years now and it seems that the problem has not been happening............Just pondering the imponderable........

[quack1]

Thanks for all the replies, at least some others have had the same thing happen.
tazman- I didn't check orientation of the brass when chambering, but I did a cerrosafe cast of the chamber-it's nice and round with no bulges and all measurements are normal.
rond- headspace is fine and I have only neck sized, without touching the shoulder, after the first loading.
Tom Meyers- when I anneal, I spin the brass with an electric drill clamped in a vise while heating.
Blue 32 and Guesser- at first I thought thin brass might be the culprit, too, but also shoot cast in 32-20 and 218 Bee and never had any cases do that.
I'm kind of leaning towards the idea that certain batches of brass do this and others don't and there isn't anything that can be done about it. Really has me curious as to what's causing it, though.
I have noticed that it hasn't affected accuracy so far, I took 5 of the worst, loaded them, and put them on paper. The group was as good as any I have ever shot with that gun, so I may just ignore it and keep loading and shooting groundhogs with them.
Thanks again for the replies.

[Scharfschuetze]

After forming, I assume that you trimed all to a uniform length, probably the minimum SAAMI spec.

I think that I'd just trim them back to the minimum again and keep on shooting. Once they work harden from sizing and shooting, you should see a reduction in the stretching I would think. It they continue to stretch like that, then I'd start inspecting the web area of the cases for case thining wich will lead to potential hull separations.

I've never ever seen this type of uneven stretching with my 25/20 loads for my Savage 23, but I do have to trim them back now and then. If you are crimping your loads for a lever gun, then a square case mouth is important for an even and uniform crimp and triming will square the lip up.

[Guesser]

As for trimming, all of the 32-20 factory brass I saw and used never grew to the minimum specified length. I've got brass that's 60 years old and it is still shorter than specified as minimum. Never could find a reason for that. Ignored it and went on casting, loading and shooting.

[quack1]

Guesser-I agree, I never have need to trim 32-20 or 218 bee either. I anneal every 5 firings and have over a dozen loadings with each, and cases are still right around minimum length, just where they started.
Scharfschuetze- as I stated in the OP, all the brass is still a few thousandths below minimum spec. They haven't stretched, the low spots on the mouths of the worst ones have shortened by .025". If I trimmed enough to square up the mouths, the brass would be at least .025" below minimum spec. If they were stretching unevenly, I'd understand, but they aren't stretching. It's the uneven shrinking that I'm curious about.

[243winxb]

The necks were annealed before forming Brass over cooked. Scrap now. Sorry.

[243winxb]

https://www.ampannealing.com/articles/40/annealing-under-the-microscope/

A good read on annealing. Note: bushing dies dont work harden the necks.

[quack1]

Brass over cooked. Scrap now. Sorry.
Worthless post. On ignore list now. Sorry

[243winxb]

I guess some folks don't like to hear they screwed up. [smilie=s:

[jsizemore]

I used to neck the 30-30 to 25 cal and did it in 1 step. Neck wall thickness can vary a bunch on commercial brass of an ancient blackpowder cartridge. Necking down in steps cut down on the number lost but could have just been the lot of brass. Even doing it in steps with annealing at each step will result in losses. When you start moving that much brass around a gentler hand is more better.

[ascast]

Worthless post. On ignore list now. Sorry

very funny thanks for the belly roll

the article is actually very good and was done by metal people, not shooting people- hence a little more in depth

[35remington]

Quack, I have seen it. To introduce my bona fides, I have more 25-20 shooting than most people. The sunken look occurs most often when oversized cast bullets are introduced into undersized case necks and I am sorry to have to suggest that annealing may contribute to this if necks are over softened. Even if the neck is expanded in a manner that would seem otherwise adequate enough, the necks may sink if too soft.

If this does not happen with .257-258" bullets in unannealed cases you have found your cause.

The fact that this is happening in annealed cases is a big clue.

Since the 25-20 operates at low pressures, it does not require obsessive annealing techniques. Once in a great while is plenty. It is especially important not to excessively soften brass when bullet fit is snug.

Your load is mild and has nothing to do with it. Soft 25-20 cases are your most likely source of the problem. Expand necks to near bullet diameter for the remainder of your cases and try again. Or load the cases with smaller diameter jacketed bullets with heavier loads several times to get the necks hard again.

I have annealed enough 25-20 brass that I can tell at a glance those got toasted pretty good, temperaturewise. Annealed case neck interiors are "grabby" and require copious amounts of interior lubricant when expanding and seating. Try a non powder contaminating wax like Lee case lube . Also consider putting the expander back in your sizing die to prevent your m die expander having to expand the full amount in a softened grabby case neck at one go.

The die mounted expander pulls out rather than pushes in.

[35remington]

To further explain, I have several 25-20 die sets from several manufacturers. The Lyman sizes full length to quite small neck interior diameter. At some point this is inconsonant with thin brass neck cases and cast bullets. The Lyman has no expander ball in the sizer, just a decapper, and expands with an M die.

See NOE for variable diameter expanders.

[beagle]

Have had a similar experience fire forming .30/30 brass to .38-55. Was using a quarter sheet of TP over powder, fill with cornmeal and seal with a dab of dacron. Fire forming down range (horizontal orientation)produced cases with one side visibly elongated. I switched to a vertical position and the problem went away. I think it may be an orientation problem./beagle

[quack1]

35- I have read the 100+ page thread on the Marlin site.
I only got irritated with a previous poster for stating I ruined the cases by over annealing even though he had no idea how I annealed them.
When I anneal a batch of brass, I use tempi-lac inside the necks of the first 5 or 6 and spin them in the flame. I get a count of how long it takes that brass to get to the proper temperature, then just heat the others by that count. Never had any problems. Although there is always a first time for everything, I'm pretty sure I didn't over heat these.
The picture of the 6 cases is not the best representation of them. The necks were pretty black, so I took a tuft of steel wool and gave it a few twirls on the neck/shoulder area to clean them, so the defects would show up better. Plus, the close-up flash with the resultant glare doesn't help, either.
I've been annealing necks for a long time and have improved my method over the years. I had an opportunity to modify an old piece of equipment to measure bullet pull, at a company I used to work for. It showed that annealing evened out the bullet pull markedly. I have been annealing all necks since then, and the extension of case life was an added bonus. I have never noticed any of the annealed necks being "grabby" when expanding or seating bullets. This includes other thin necked cases- 32-20 and 44-40.
I have been expanding with M dies machined .002 smaller than bullet diameter ever since I got a concentricity gauge. Bullets show less runout when only using the M die to expand, then when pulling the neck over the expander button on the deprime stem in the die.
That said, using both expanders may help stop my uneven necks with this particular brass.

It will be easy to try some un-annealed cases. I had 200 pieces 32-20 brass and only formed half into 25-20. I'll take some and form to 25-20 without annealing, load and shoot 3 times, just as I have done previously, and see if the mouths stay square. It may take me several days to shoot the un-annealed cases 3 times. My range time has been limited by the nearly every day rain we have been having this summer.
Some measurements of my brass:
Fired case neck OD-.279
Sized with M die, neck OD (same case) .265
Bullets drop from mold at .260. Since they chamber with no resistance, I just lube and shoot them unsized.
I machined the M die .002 less than bullet diameter- .258
Expanded neck ID- .258 (This measurement taken with calipers, all others with a micrometer)
RCBS die expander button diameter-.255
As I said in a previous post, so far, the shrinking hasn't changed the accuracy, and since that's always my main goal, I'll just keep using them.
After over 30 years working in research, I guess I just can't help wondering what causes things to happen.
Again, thanks to all for the replies.
I will post what happens when I use un-annealed brass.

[35remington]

I agree with pretty much everything you said and do things much the same way. Thing is....25-20 necks are thin, and thin annealed necks are weaker than thicker annealed necks.

Quite true the M die produces less runout. But more runout still often produces good groups as the cast bullet itself is often the limiting factor. Some of my most extensive runout testing was with cast bullets and 25-20 cases, and bullet seating depth had more to do with achievable accuracy than reasonably large differences in runout did.

What I am suggesting is that if what you are doing is somehow causing this, do it differently with a small batch of cases and see what happens. Most 25-20 dies size the case neck interiors quite small, and everything you are doing is pushing inward on the case including neck expanding and bullet seating.

Reverse that. Pull an expander out for awhile instead. Size the bullet to .259." Load skinnier jacketed bullets sans the M die with the regular expander. Flare the mouth with needle nose pliers. Work toward reducing frictional fit interference in the softened case neck. If you apply two cures at once you may have to guess which one was more helpful.

The M die is an expander. The bullet is an expander.

I can show you a number of my oldest cases that have some degree of uneven case mouths. It is not as bad as yours, and some of them have such a long reloading history I cannot tell you exactly what point it happened, but to my recollection most of them were annealed at some point.

My rifles shoot best with very short jump to rifling and I am not all that convinced that even bullet pull is all that necessary but I suppose that opinion may not be all encompassing. My rifles have shot many loads with quite old unannealed cases and accuracy is apparently unaffected.

In any event, the Reader's Digest version is that if something occurs after doing something else, modify what you suspect to be the contributing factor. The second action (loading the ammo) apparently may cause the case deformation, so change what you are doing in the way of frictional forces applied to a softer case neck and see what happens.

[quack1]

I said I'd post new results when I got them, so here they are. They might be of interest to other posters that said they got uneven necks.
I took 10 32-20 cases from the same lot as previously used and formed ten 25-20 cases without annealing. I lost one to a badly folded neck. They were then trimmed to minimum length and loaded and shot 3 times, same load, loading method and lot of bullets as the previous post. The only thing different was skipping the neck annealing. Accuracy was the same. Three cases showed the same uneven necks, while still measuring slightly under the trim length. They looked the same as the pictured cases in the original post. The shortest part of the necks were roughly .020 shorter.
I then took ten more 32-20 cases and, without annealing, formed them to 25-20. Lost another to badly folded neck. After trimming, I then loaded them, same as before, except I used the expander button on the deprime stem to expand the necks. I belled them with a tapered punch to start the lead bullet. After 3 load/fire cycles, two necks showed some unevenness, but after measuring, the unevenness was caused by part them stretching about .009 over the minimum trim length, opposite of the previous test. Pulling the ten cases over the expander button took noticeably more force then just expanding with the M die. Accuracy was poor, the 10 shot groups were over twice the size of groups from the other two tests. The poor accuracy probably came from the overly tight and or crooked necks from using the only the expander button on the deprime stem. I checked concintricity after seeing the first poor group, and the worst runouts were in the .012-.014" range. Normally, runout was .003-.004".
I didn't try any jacketed bullets as I have only ever shot cast in this gun and simply don't have any jacketed.
With some (20%- 25%) of the brass either shrinking or stretching unevenly in each test, I'm inclined to think that this particular lot of brass is causing the problem. Maybe it's the brass composition or something in the process used at the factory. Also, since 218 bee, 32-20 and 44-40 brass I have used, loading them with pretty much the same methods, never showed any tendency to acquire uneven necks further leads me to question this lot of brass.
Using the expander on the deprime stem does show the least deformation of the necks, but the poor grouping from that test makes incorporating that change to the loading process worthless.
Again, many thanks for all the replies.