Stuck Case in Chamber

The reason nobody is giving you a temp is because it depends what you want out of your annealed cases .

The general rule, brass is fully annealed when placed in a heat source of 600* for one hour and grain structure starts to change at 450* to 475* . That however is not firearm cartridge brass but rather a big hunk/block of brass . Cartridge brass is MUCH thinner and can be reach that 600* much faster and then there's the fact you don't want the whole case heated to 600* so you never just toss the whole case into the heat source . This changes everything when it comes to annealing cartridge brass and one size / temp / duration in heat source is likely to change based on what you are trying to accomplish .

Don't quote me but I think the AMP machine heats the case up to about 950* in about 1.5sec while the torch method usually heats the case to about 750* in about 4 to 7 seconds depending on flame heat or if two torches are used .

Now IMHO yes you can and no you can't ruin cases by "over" annealing . Again it depends on what you're trying to accomplish when annealing your cases . I'm going to throw out some temperatures here but they are general examples and likely differ some but the general point is valid . Bench rest guys tend to want there cases fully annealed to what I call dead soft . Which basically is "annealed as much as it can get which is what the AMP does . If it heated the case to 1050* or 1100* rather then 950* , the case would not be significantly more soft . How ever if you only heat your case to 550* to 600* the case will be stress relieved but not fully annealed . This is what I do or more specific I heat my neck and shoulders with a torch to 750* based on a temperature indicator applied to the case before heating .

I choose 750* to stress relieve my cases only which does return them to a more consistent bullet hold . However if I wanted the best consistency I would fully anneal them and they would be virtually identical from case to case . I did some testing on this idea and found when I fully annealed case necks I had to little bullet hold to use those cases in my auto loading/semi auto rifles . I have real concerns that fully annealed cases in a AR-10 for instance will have to little bullet hold and the bullet may be set back into the case when being slammed forward into the chamber by the BCG . That is the main reason I don't fully anneal but do anneal for my AR-10 and 5.56 rifles . These firearms are hard on brass especially my AR-10 so annealing is helpful if I want more then 3 loading with my brass . Keeping all that in mind , then I say yes you can over anneal a case . However if you're single loading by hand you don't need that much bullet hold and fully annealed cases are not an issue and in actuality more desirable for better consistency .

So in some circumstances you can over anneal and ruin the case for the purpose you intended it .
 
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Metal God, your explanation basically follows along what I have thought about annealing cartridge brass. It just bothers me when someone tells me the brass at say, 950-1000 degrees is a total loss because it can't be saved. And does not offer an explanation of the mechanics that make it so, is irritating. I am all for learning new things.

Completely annealed cases in a semi auto probably would be a bad idea, but for a bolt gun that only sees the range, I don't see where it will matter. For me, annealing then sizing and expanding will definitely begin to work harden the necks and. Actually allow for pretty consistent bullet grip.

I will do more tests with my cases and the powder charge, bit I really do not believe that my powder share is a problem.
 
Interesting issue.

One factor may be that when a case has zero head clearance (the gap between the bolt face and the case head created when the firing pin punches the whole cartridge forward) there is an increase in bolt thrust because of the time delay associated with stretching the head back through the head clearance is absent. That delay often allows the pressure to pass its peak before the case head contacts the bolt face, thus providing a lower peak pressure. The difference isn't huge; on the order of 20% or so (based on Varmint Al's analysis) but it can be enough, for a load on the pressure edge to stretch the chamber length a little at the pressure peak. When the chamber subsequently springs back to its normal length, it clamps down on the less elastic brass case, which doesn't spring back as far, compressing it and creating the "sticky" bolt lift experience.


I am curious to know how one over anneals a case neck. It would stand to reason that soft is soft. In fact I believe that heating the neck just enough, will cause more variation in bullet grip, than if you had heated slightly more than enough. I will admit that it is possible that the shoulder was annealed about the same as the neck. Which I do before I sized the cases. I do this to allow the neck and shoulder to work harden as I manipulate the dimensions of the case.
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The short answer is that heat and time great enough to cause grain growth should be considered over-annealing as it weakens the brass.

The long answer: Below is information I gleaned mainly from the reference cited at the bottom of this post and matweb.com's data on cartridge brass (aka, 70/30 brass, 260 brass, and UNS C26000 brass). I have included linked definitions from Wikipedia, which explains adequately for the sake of understanding the principles involved.

Annealing has three stages. In order of ascending required time × temperature, these are Recovery, Recrystallization, and Grain Growth. When you work brass, it deforms grains, putting a lot of potential energy into them (like cocking a mainspring), and their push to move to a lower potential energy position puts the brass under stress and the threat of cracking if the cumulative stress from working it gets high enough. Recovery moves these atomic level dislocations to lower potential energy positions, thereby relieving the stress.

Recovery can be observed even at boiling water temperature, but it takes weeks at that temperature and you wouldn't want a long heat exposure because of the risk of stress-relieving the heads. You want the heads hard because the tensile strength of the hard brass (yield point) is greater, better enabling it to withstand pressure. Raising a case neck even to the temperature of candle flame heat will stress-relieve it n 20 or 30 seconds if the neck is highly work-hardened. If it isn't, little will happen, but in that case, little needs to happen.

You can heat brass beyond recovery time and temperature to cause recrystallization. This makes the grains regrow from the beginning, and as long as you minimize the heat exposure to just accomplish the job, the grains stay small and the tensile strength of the brass is as good as soft brass tensile gets. Unlike recovery, which requires X-ray diffraction to "see", recrystallization can be seen in a metallograph, as can grain growth.

Heating still further (red heat sustained for enough time) causes grain growth. This is where the individual grains increase in size, reducing the total amount of grain boundary area. That reduction weakens the brass (tensile strength goes down), and a thoroughly annealed brass with grain growth can be easily indented with your thumbnail because it is so weak. A feed ramp can bend it too, making it undesirable. Such brass is over-annealed for practical purposes, but also for another reason described further down.

For shooting purposes, the cartridge case brass grain size is fine as it comes from the factory, so recovery (aka stress-relief) is all you need to keep brass shooting.

Some complicating factors:

How much annealing time you need at any particular temperature or how much temperature you need at any particular annealing time depends on how much stress is in the brass to begin with. For example, at a given temperature a piece of 75% work-hardened brass will go through recovery or recrystallization and be done about nine times faster than a piece of 50% work-hardened brass will¹. Brass in case necks that are about to split are close to 100% work-hardened, based on the very small elongation at break that splits them, but brass that has only been resized once since annealing isn't that close to being that hard. So, an annealing time and temperature just large enough to quickly anneal a piece of nearly 100% hardened brass does almost nothing to a piece that has only been resized once after the last annealing. The brass will have to reach a certain work-hardened threshold before that same time and temperature exposure starts to affect it. When it does finally reach that point, then annealing every time you load will keep the brass at a constant hardness level, but whether that has any practical value is questionable. Bryan Litz got the use of one of the AMP annealers and ran two halves of a lot of new brass side-by-side for ten reloading cycles. Half was subjected to the AMP annealer every load cycle, while the other was not annealed at all. At the end of the test for velocity consistency and performance, the unannealed brass actually did slightly better, but not by a statistically significant margin.

Properly annealed brass should last ten to as much as twenty load cycles (depending on how much you work the neck each time) before it needs to be annealed. Indeed, this is part of Norma's QC test, according to their 2013 hard copy manual, checking that each piece lasts through ten firings and loadings as it comes from the box. Brass that has been weakened by overheating and grain growth will have its smaller grain boundary area stressed more by the same number of resizing cycles, and thus may only last three to five reloads before it has to be annealed again to prevent splitting. Recovering a piece of over-annealed (significant grain growth) brass requires work-hardening (resizing again will do it, as demonstrated by Eric Cortina in this video) and then heating until recrystallization occurs, which re-reduces the grain size, but heating no further so the grains stay small. This will restore tensile strength and provide longer load life without annealing again.

Finally, if you wade through the different temperings of cartridge brass in Matweb's data, you discover something counterintuitive: increased brass hardness is associated with increased tensile strength and shortens its elastic range, but as long as you are stretching the brass within that elastic range, the modulus of elasticity (how much force it takes to stretch it a given percentage) stays the same. This means a case neck that is 90% work hardened and one that is 20% work hardened and both with bullets seated that expand the neck 0.001" will both hang onto the brass with equal strength (equal "neck tension"). This is the main reason Litz saw no change in performance as his brass got harder.

The bottom line is, you can anneal or over-anneal brass almost as much as you want without changing the start pressure it gives the bullet. You can't over-anneal without weakening it, though, and reducing the number of load cycles it will give you between annealings and before it starts to split. But you can still recover brass from an over-annealed state by work-hardening it and putting it through recrystallization without going all the way through grain growth. Annealing beyond mere strain-relief is unnecessary for brass whose grains are a good size and helps avoid accidentally annealing until the grains grow. It also reduces the amount of surface zinc loss you get from the heat, though I doubt most shooters run brass through enough load cycles before they toss it to have that matter, I haven't tested that hypothesis.

It is worth noting that, with all the brass prep work they do, many benchrest shooters coax upward of 50 reloads out of their brass. If you don't overwork the brass, as by using bushing or collet dies on the neck sized so no expander is required, that can happen. Board member Hummer70 has one .308 case that has been reloaded over 150 times and still works.


In this instance, I was not actually pushing the shoulder back at all during the sizing operation.
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If the cases came out of the die the same size as fired cases come out, then you set the shoulder back a little. This is because, when the case touches the sides of the sizing die it squeezes it down narrower and longer. If there was no shoulder contact with the case, it should come out longer than it was coming out of the chamber.


¹Recrystallization Behavior of 70/30 Brass, John Klein, U of Chicago, Dept. of Civil and Materials Engineering, CME #470, Jan 12, 2016
 
I always follow 3 simple steps in brass maintenance

1) I keep all the brass on the same anneal. Either never anneal or anneal every firing. It takes so little time I just anneal every firing. By annealing I mean stress relief or slightly softening the brass. I simply do not let it get hot enough for a full anneal. The only time I ever had any issues was when I mixed a lot of brass together that had different numbers of firings. I had a lot of oddball high/low flyers. A simple flame anneal cured that issue

2) I size so that the ID of the neck is .003 smaller than the bullet I am loading

3) I set the shoulder back .003 shorter than what it was when it entered the sizing die

just those three steps gives me very consistent neck tension and brass behaviour

here is a link that explains the difference between stress relief, softening/annealing, full annealing and flash annealing

https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/brass---stress-relieving

an oldie but still relevant article on 6mmBR

https://www.6mmbr.com/annealing.html
 
kilotanker22 said:
So I might have goofed up a little.
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Two mistakes I can identify:

The first and biggest was not bringing a clearing rod to the range. Always, ALWAYS bring a clearing rod to the range.

The second was probably not trimming your brass all the way back to recommended trim-to length.
 
Unclenick said:
Heating still further (red heat sustained for enough time) causes grain growth. This is where the individual grains increase in size, reducing the total amount of grain boundary area. That reduction weakens the brass (tensile strength goes down), and a thoroughly annealed brass with grain growth can be easily indented with your thumbnail because it is so weak.
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I'd like to know what that temperature and duration is because I've gotten some necks pretty damn hot and never notice them to be so soft a thumb nail could cause an indentation ?

I did a bunch of tests years ago on annealing and purposefully left cases in the heat WAY longer then you ever should . I had planned to size and load them all up to see the differences over annealing has on the cases . I never got around to doing that but I did mark and separate all that brass and saved it all . Guess I'm going to need to go find it and see how soft the uber over annealed cases actually are .

This is one example of my testing , I kept the neck and shoulder in the torch flame long enough to melt the 450* Tempilaq applied close to the head of the case . These were both LC cases in 5.56 & 308 . If I recall the necks and even some of the shoulders were glowing red for a few seconds in a brightly lit room to get the heads to a temp of 450* . As you can see a few don't seem to have gotten hot enough to melt the 450* indicator but I assure you all the neck and shoulders were heated to a temp well beyond what is needed . FWIW that is 750* Tempilaq just below the shoulders .

z1mr.jpg


Unclenick said:
Finally, if you wade through the different temperings of cartridge brass in Matweb's data, you discover something counterintuitive: increased brass hardness is associated with increased tensile strength and shortens its elastic range, but as long as you are stretching the brass within that elastic range, the modulus of elasticity (how much force it takes to stretch it a given percentage) stays the same. This means a case neck that is 90% work hardened and one that is 20% work hardened and both with bullets seated that expand the neck 0.001" will both hang onto the brass with equal strength (equal "neck tension"). This is the main reason Litz saw no change in performance as his brass got harder.
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Just so I understand , are you talking .001 of stretch/expansion when seating the bullet and it will have the same hold or .001 expansion on ignition/release of the bullet will take the same energy/force to expand the neck to release the bullet ?

I know it was either you or maybe Bart B that said long ago something like . Even using a standard sizing die without the expander will you give you consistent bullet hold because you've sized the neck down so much that seating the bullet actually expands the case neck similar to an expander does . Meaning .001 / .002 / .003 bullet hold may actually offer different neck tensions at each increment but there's a point at which you've sized the neck to far and the only way the bullet can be seated is if the bullet it self expands/resizes the neck to allow the room for the bullet ? Putting it another way would be to say a .007 bullet hold will give you the same neck tension as a .010 bullet hold because both needed to stretch the neck beyond it's elastic ability to the point of resizing it again ??
 
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Recommended trim length is max minus .015" for this cartridge. I still trim all of my brass shorter than max case length. Also worth noting is that first fired factory was about .003" longer than my trim length prior to being sized. I believe that any trim length within specification is fine as long as it is consistent.
 
I annealed and properly sized a number of cases today, loaded them and headed off to the range today. Two things stood out to me.

First, the heavy bolt lift problem went away.
Second, I saw an increase in average velocity by 30 fps vs my last trip for the same powder charge. This string had an extreme spread of 53 fps. I had thought ahead and loaded some with half a grain less powder. The next set of seven shots mirrored the data I had recorded from my previous trips with the other load. I decided that I must have made an error when recording data at some point in the line. Sure enough the second time I recorded data for this load, I wrote the wrong number in my book. It was only half a grain difference, but there it was.

Twice in a two week period I had written the wrong number when keeping notes. I now believe that my issue was caused by a combination of improperly sized brass, and poor note taking, resulting in me measuring the wrong powder charge.

My take away is this could be a good lesson in the importance of keeping accurate notes. Two mistakes in a short period of time could have been prevented by more attention to detail in note taking. Also, it is unlikely that I would have discovered my two mistakes if I did not keep notes to begin with. I can own a couple mistakes. For me the main goal in anything is finding the truth, even if is something I din't want to see
 
Just so I understand , are you talking .001 of stretch/expansion when seating the bullet and it will have the same hold or .001 expansion on ignition/release of the bullet will take the same energy/force to expand the neck to release the bullet
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The more you stretch the neck the more energy it takes. A neck tension of .002 takes twice the energy than to stretch a neck .001 etc. You also have a small amount of hysterisis to take into effect, which is when a value of a physical property lags behind changes in the effect causing it. When the bullet leaves the neck that stored energy is released

Here is easy to see example is in this video and is also explained in the comments.


https://www.youtube.com/watch?v=fFtM9JznLh8

edited for clarity
 
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Dawg I get that to a point but at what point does the rubber band over stretch it’s ability to return to it’s original length/size . It’s at that point and beyond that the energy being stored does not increase as that concept relates to cartridge brass correct ? Same with the case neck , if you stuff a .308 bullet into a .243 neck you don’t end up with .065 of bullet hold/neck tension . In that case like ghe band you will have actually changed the size of the neck by resizing it with the bullet . This of course is an example to make a point not to say you could actually seat a 308 bullet into a 243 case with out collapsing the shoulder . Put another way if change a 308 case to a 243 case buy FL sizing it down to have .003 neck tension of your loaded cartridge . When seating your 243 bullet into that once 308 case you sized down to have .003,bullet hold . You don’t have .060 + the .003 of bullet hold because you’ve sized the neck down beyond its limits to spring back correct ?
 
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The reason I left the cases longer and trim every time was to leave a little more case neck to grip the bullet. Probably doesn't make much difference, bit I don't r really see how it could hurt.
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As long as the length is consistent, shorter is not an issue.

How much variation in that which would make an accuracy difference I have not a clue.

I would think the other variables would mean .005+ might not show but that is an opinion not based on anything other than so many variables go into an accurate load the end goal is as consistent as you reasonably can.
 
UnclenicK

Trying to clear up some of the Anneal aspects.

Realistically if you overhead just the case neck/shoulder, can you ever get the grain structure back by shooting?

And the neck splits I thought were a result of no annealing and the right anneal maintains the grain structure at that end of the case and remains resilient.

I have shot what I believe were over annealed cases and no issues other than the tension seemed low. Maybe not good accuracy but not a dangerous aspect (double ensuring that I mean Neck/Shoulder and not the body or base.
 
There is a lot of good conversation in this thread. The attention you all have given this is excellent!

I am gonna have to experiment and research more into the properties of the brass and how the grain structure is affected by heating and working the metal. I find this to be an interesting and not well understood concept throughout many that I have talked to. Admittedly, I do not understand the mechanics by which these types of metal work that well. I know that I am not getting my cases hot enough to ruin them. I also know that different levels of annealing do not yield the same level of hardness. As evidenced by being able to change the shoulder location of sized brass. By only changing the time and temperature that each case is subjected to. This is when annealed prior to sizing. A fully annealed case can have the shoulder pushed back several thousandths more than a case that has been work hardened with the same die setting and preparation process.

My goal in this post is to learn how to fully anneal the case necks prior to sizing. Without increasing the grain structure such that the neck cannot be repaired by sizing to work harden. The goal is to also not ruin my cases by getting split necks or damaging the body or head of the case.

Thanks everyone, I very much enjoy meaningful conversation.
 
MG,

What you are describing is called the material's yield point. Materials usually are elastic over some range. When you stretch them beyond that range, they no longer fully return to shape, and you have exceeded the true elastic limit and have begun to yield.

A typical stress/strain curve is on this page. Click on the upper one to see the image more closely and the regions defined. Basically, the stressing force applied is increasing as you go up the vertical axis of the curve, and how far it strains (is deflected as a result of that stress) is shown along the horizontal axis. Such a curve is made by taking a sample and stretching it and plotting force vs. displacement. It's a one-way test, as it goes beyond the elastic range, at which point displacement is greater per change in the stress force, and it will even stretch to the point it becomes weaker and less stress is needed to achieve additional strain (the downward turn in the curve toward the end).

What happens with brass is when you stretch it further than it will spring back, you have exceeded the yield point and the curve has flattened, meaning it will take a lot less additional force to continue the stretch than it did in the elastic range. At that point there is still some increase in the hold on the bullet, but not nearly proportional to the amount of stretch. In other words, if you have a case neck that springs back about 0.0015" after expanding with either a bullet or a mandrel, you can figure it will take X amount of force to expand it half a thousandth, and 2X force to expand it one-thousandth, but then you start getting into the yield range so it takes less than 3X force to get to one and a half thousandths and only a little more to get to two thousandths from one-and-a-half thousandths and even less additional force to get to three thousandths from two. Eventually, you hit that turn in the curve and then the next 0.001 of expansion actually has less hold on the bullet.
 
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