Stuck Case in Chamber

[Metal god]

Originally Posted by Unclenick

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.

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 .

Originally Posted by Unclenick

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.

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 ??

[kilotanker22]

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.

[kilotanker22]

Unclenick, great info as usual. Your time and attention to detail is much appreciated, Thank you

[kilotanker22]

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

[hounddawg]

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

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

[Metal god]

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 ?

[hounddawg]

https://bisonballistics.com/articles...tress-analysis

A worthwhile read from a very knowledgeable shooter

[RC20]

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.

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.

[RC20]

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.

[Metal god]

hounddawg , that link does not work for me . What's it about ?

[hounddawg]

fixed the url , try it now

also another by Damon on the hows and whys of annealing

https://bisonballistics.com/articles...rass-annealing

[kilotanker22]

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.

[Unclenick]

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.