Have you had any experience with "cold welding" of bullets in case necks?

[jlow]

AFAIK, it is impossible for a moly coated bullet to cold weld to a case at least based on the definition of cold welding.

Now that does not mean that there could not be another mechanism that cause the moly coated bullet to stick to the case, this is why if we really want to understand what is happening, we need to measure the adhesion forces involved (not just pop or no pop), and then disassemble the pair and look and analyze the interface. Without detailed analysis, it could get very confusing - which is why we are where we are right now.

 

[Flat Land Shooter]

I believe this is part of "press fit friction force" and if you google it this is what you will find.


[PDF]
INVESTIGATION OF THE PRESS FIT JOINTS BY THE TRIBOLOGY ...
facta.junis.ni.ac.rs/me/me2001/me2001-15.pdfFile Format: PDF/Adobe Acrobat - Quick View
The strength of a press fit joint represents static friction force that is the biggest force that ... Key words: tribology, press fit joints, friction force, friction coefficient. 1 .

 

[jlow]

I believe “Press fit friction force” would certainly be part of the force responsible for holding a bullet in a case which as an ID smaller than the diameter of the bullet. However, this force should be relatively constant not change appreciably over time.

“Cold welding” would be an additional force on the bullet that develop over time and slowely increase the force holding the bullet.

 

[BoydAllen]

Flat Land Shooter,

Two things: Have you had the experience of seating bullets shorter in reloads that are a couple of years old, and had some of them take a great deal (perhaps 10X) or more force to move the bullet, and when it moved there was a loud pop? The second thing is that I have referred to this as cold welding because that is the term that has come into common use for this phenomenon. Not being a metallurgist, with a lab at my disposal, I have no way of verifying what actually takes place. Let me sneak in one more thing. I think that it is obvious that in the case of coated bullets, that it is unlikely that welding would occur, but the same results have been observed, so it may be that there is more than one way that bullets get stuck.

I started this thread for a couple of reasons. If I post something that a reader has not experienced, and he has been loading for a number of years, it may be discounted as some sort of mistaken observation, or conclusion, but if there are a number of such reports, then it is more likely to be taken seriously. The other reasons are so that shooters may be made aware that if they are going to load well ahead of their shooting needs, that this should probably be addressed. The fact that this thread has attracted someone with the expertise and facilities to do a detailed study of the pieces that were bonded is an unexpected bonus.

Boyd

 

[jimbires]

I've looked high and low , I can't find the ones the necks were stuck on . I must have thrown them out . Jim

 

[bozo699]

AFAIK, it is impossible for a moly coated bullet to cold weld to a case at least based on the definition of cold welding.

Now that does not mean that there could not be another mechanism that cause the moly coated bullet to stick to the case, this is why if we really want to understand what is happening, we need to measure the adhesion forces involved (not just pop or no pop), and then disassemble the pair and look and analyze the interface. Without detailed analysis, it could get very confusing - which is why we are where we are right now.

Boyd,
PLEASE change your title, for some reason the scientist in jlow CAN"T get cold welding out of his mind, It's a gall darn "POP" we call it cold welding for a lack of a better word, I have repeatably told him this but to no avail. I know for a FACT that cold welding , hot welding, fusion, stuck bullet, Alzheimer's, or whatever, the pop is there at times to save further confusion and my blood pressure PLEASE change the title to anything in the world but
"cold welding"
Thank you,....your good friend,
Wayne.

 

[jlow]

LOL! Wayne, you got to chill out, it’s not worth getting riled up about this type of stuff.

 

[BoydAllen]

Wayne,
As long as reloaders learn that there is a potential problem, and what they can do to avoid it, I am happy. If someone wants to take it farther than that, so much the better. As far as a name for what we are talking about goes, I am open to suggestions. Let's have some fun with this. I am sure that someone will come up with a phrase that converts to a catchy acronym. Of course we can take a clue from the world of entertainment an simply change the name to "formerly known as cold welding" ;D

As far as changing the title goes, titles are supposed to be hooks that grab potential readers, motivating them to look into what lies beneath. Have you looked at the stats for this thread? If all my posts got that much attention, I could start charging for coming up with titles

Boyd

 

[jlow]

Wayne, I realized that my scientific tack has not been what you are looking for, but seriously, can you tell us what you personally is looking for in terms of answers?

 

[bozo699]

Wayne, I realized that my scientific tack has not been what you are looking for, but seriously, can you tell us what you personally is looking for in terms of answers?

Yes sir the only answer I am looking for is find out what causes a problem and fix it, don't do it anymore etc. etc. In this case Boyd started the topic " Have you had any experience with "cold welding" of bullets in case necks?"
I have had this happen so I responded, I know, not think, I know what caused my problem it was to clean of necks, I polished them with steel wool, I only had .001 neck tension and I had un waxed mollied bullets, that's all the more scientific answer I needed, I don't know nor care the particulars I just know that combo is a bad thing, I had some 6.5*284 winchester rounds loaded the same way from a match over a year ago and I recently tried to reseat them and got the same "POP" so it's not a maybe for me but a FACT!! I apologize for getting so worked up but it seems your hung up on cold welding and the things that cause it and the things that can't cause it when were not talking about cold welding here at all!! were talking about a POP noise when reseating bullets, those of us that have heard it, it is unmistakable and we KNOW it has happened, not think but know!! so the term cold welding was a miss thought, miss terminology, or just a lack of a better term or word IMO Anyway rant off and I apologize to all for my rantings I just don't understand I guess, and yes Boyd you have got some mileage out of it for sure, my Wife said you called while she was on a long distant call today and forgot to tell me until now, she ask me who I have been typing to for the last three hours, when I said a reply to one of your posts she told me, I have been writing this half the night I wouldn't be surprised when I hit post there have been multiple replies, I will call you tomorrow when I get off my track hoe.
Wayne.

 

[BoydAllen]

Wayne,
I really appreciate you sharing your experiences on this thread, as well as on the phone. The information that you have provided is exactly what I was looking for when I started the thread.

As an aside, today I spoke with an old friend who had just picked up an ultrasonic cleaner from Harbor Freight, and after he told me what a good job it does of cleaning all parts of cases ( A friend who has one told him.) I told him about the subject of this thread. He is eleven years older than I am, and does not use the internet. He had no idea. I think that I may have done him some good, because he loads a lot of rounds at once, and they may sit on the shelf for a long time. Without the information that you all have provided, he might have just thought that I was exaggerating, since he has never read of this in a magazine. As it stands, I think that we have possibly saved him from a big problem.

 

[bozo699]

Wayne,
I really appreciate you sharing your experiences on this thread, as well as on the phone. The information that you have provided is exactly what I was looking for when I started the thread.

As an aside, today I spoke with an old friend who had just picked up an ultrasonic cleaner from Harbor Freight, and after he told me what a good job it does of cleaning all parts of cases ( A friend who has one told him.) I told him about the subject of this thread. He is eleven years older than I am, and does not use the internet. He had no idea. I think that I may have done him some good, because he loads a lot of rounds at once, and they may sit on the shelf for a long time. Without the information that you all have provided, he might have just thought that I was exaggerating, since he has never read of this in a magazine. As it stands, I think that we have possibly saved him from a big problem.
[/quote
Boyd,
You are welcome, I have learned so much from you this has made me happy to be of maybe some assistance to you in this matter, I also apologize to you as I know you are a layed back intelligent man and don't particularly care for my barbaric approach to things, jlow I believe is a intelligent and interesting fellow also it's just we think in opposite directions, he frustrates me as much as I probably frustrate him, it just seems to me he doesn't hear or doesn't understand the problem as he seems to have a one track mind focused only on "cold welding" at any rate this has been a good thread and I am really glad you may have diverted a potential disaster for you friend, I think maybe he can use his ultrasonic cleaner but will have to learn what will need done to the necks after cleaning, I still steel wool my necks after I inside ream them but have learned if I vigoursly brush the necks with a nylon brush they seat okay and no POP a few weeks later but I am not using moly either but I may try that to see what happens, I do know brushing is key, after ff is done I never use steel wool anymore I learned my lesson there for sure, please let me know how your friend fares out with things, If I knew you were going to be up so late I would have called you anyway,...talk to you tomorrow my friend.
Wayne.

 

[jlow]

Thanks Wayne! Yes, I have been accused of having a one track mind before but it is usually about something else – LOL!

But seriously, the reason that I continue to focus on cold welding is because it is (as you say) the topic of this thread. I understand now why you are frustrated since your rounds are in fact use molly coated bullets that has that “pop” problem and I try to dissuade people talking about this but my rationale for doing so is because when one tries to do fact finding about a specific phenomenon, a lot of similar things frequently gets pulled in even though it really has nothing to do with the actual phenomenon one is talking about. When this happens, the discussion goes ten different ways and you don’t really get anywhere since it gets diluted and too confusing for those reading it.

My suggestion in a situation like this is to start a different thread which specifically focus on what you are seeing.

 

[bozo699]

Thanks Wayne! Yes, I have been accused of having a one track mind before but it is usually about something else – LOL!

But seriously, the reason that I continue to focus on cold welding is because it is (as you say) the topic of this thread. I understand now why you are frustrated since your rounds are in fact use molly coated bullets that has that “pop” problem and I try to dissuade people talking about this but my rationale for doing so is because when one tries to do fact finding about a specific phenomenon, a lot of similar things frequently gets pulled in even though it really has nothing to do with the actual phenomenon one is talking about. When this happens, the discussion goes ten different ways and you don’t really get anywhere since it gets diluted and too confusing for those reading it.

My suggestion in a situation like this is to start a different thread which specifically focus on what you are seeing.

That is exactly what I have been trying to tell you my friend, forget about the word "cold welding" and concentrate on the problem,.......A,......" pop",....when reseating a bullet! I still believe Boyd used the phrase for a lack of a better word or maybe he thought that is what it was but we have now learned due to this thread that can't possibly be the case here because;

Cold or contact welding is a solid-state welding process in which joining takes place without fusion/heating at the interface of the two parts to be welded. Unlike in the fusion-welding processes, no liquid or molten phase is present in the joint.
Cold welding was first recognized as a general materials phenomenon in the 1940s. It was then discovered that two clean, flat surfaces of similar metal would strongly adhere if brought into contact under vacuum.

cold welding
n.
The welding of two materials under high pressure or vacuum without the use of heat.

Since most precision shooters are using around .001 neck tension, The Powder Boyd uses maybe .004 neck tension , I can and have seated a bullet with my calipers and ojive measurement tool with tension around .001 so obviously high pressure isn't involved, we also learned according to the anodic index copper and brass are to close to the same to have galvanic corrosion going on,...SO :cold welding" is OUT!! arguing the point would be like arguing why is the paint falling off all 9 Dodge pickups I own, it's a fact the paint is falling off but it has NO BEARING on this thread and neither does cold welding,...SOlets get onto the subject at hand,.....A "POP"is being heard while reseating bullets in cases, some has set around for years and others only a few days, we know in one instance for SURE that it was caused by overly clean necks or polished necks with steel wool, steel wool particles probably left in the case neck and molied bullets that didn't have the original neco process of waxing done to them with .001 neck tension on multiple times fired brass, I have also had it happen on non mollied bullets but never knew what was going on and had long forgot about it until Boyd started this thread, the reason it stuck in my mind this time is because it was at a match last year and several people commented why was I running so much neck tension? I said I wasn't and then the discussion started and we talked about it quite a bit but never came up with a answer so again I forgot about it until Boyds question, Boyd and I talked about it at length on the phone, since it has happened to others without the use of moly that isn't a requirement but we believe ultra clean necks are a definite culprit of the phenomena and I personally believe that possibly a combo of to clean of brass and dirty at the same time by leaving steel wool particles in the neck may be a factor at least in my case since two documented cases for me involved the use of steel wool but only one set of bullets were mollied so let's investigate the "POP" and stop worrying about cold welding and the paint falling off my pickups
Wayne.

 

[BoydAllen]

There could be more than one cause, one that is the case with uncoated bullets, and somthing slightly different with coated. I think that my friend may have been onto something when he mentioned the forming of a shared oxidation layer. This would explain the reason that necks that have been polished bright seem to increase the probability of the problem. Once there is a skin (layer of oxide) on the metal, the base metal is effectively insulated from further oxidation. In the case of stainless steel, I believe that this is referred to a passivation.
http://en.wikipedia.org/wiki/Passivation
Unlike bimetallic corrosion there does not need to be a potential between two materials for a shared layer of oxidation to form....I think. My friend, the materials engineer would be the man to explore this with. In any case, I think that it is highly likely that tiny scratches on the oxidized surfaces of the bullet and the case may happen as the bullet is seated, exposing fresh metal that may form this common layer at those points.

 

[jlow]

Wayne, I am glad that I understand where you are coming from, but think you only read the first half of my post – LOL!

I think if there was only one cause i.e. only with molly coated bullets, we can call it quit and start a new thread. However, I think BoyAllen is likely right i.e. there is likely more than one situationa and more than one cause and it could be this idea with “shared oxidation”. This is why a physical microscopic examination of the joint between the two components that may have welded together would shed a lot of light. If it was cold welding, one would see the physical joining of the two metals. If it was shared oxidation, one would see a layer of oxidation between the two metals.

 

[BoydAllen]

Since one of my goals for this thread was to spread the word about the "bonding" of bullets to case necks, I think that as long as coated bullets have the same problem, that they should be included in this thread, even though the mechanism that causes the problem may not be identical. Many shooters have learned that there is a potential problem, and may learn of ways to possibly prevent it.

 

[jlow]

That of course would be fine! 8) I was only trying to help with suggestions as we might reduce confusion and not to dictate what should be done.

 

[Flat Land Shooter]

Boyd - have very little experience in reloading, but many years experience in hydraulic manufacturing. My experience leads me to the difference between "Static Friction" and "Kinetic Friction" Any time to parts have a press fit and are assembled and the assembly process is complete, it takes more force to put one of the parts in motion again that it took to put them together the first time. I believe the "pop" is the result of one of the parts being put into motion. If you look at the data and charts in the article I referred to in my earlier post you will see the force increases to make one of the parts move.

 

[BoydAllen]

Flat Land Shooter,
Here is the deal. You can go back and shorten the loaded length of previously loaded ammunition, and it may take a little bit more umph (Excuse the highly technical language.) to start the bullet moving, but not much. What we are discussing is something entirely different. By some mechanism, the bullet becomes BONDED to the case neck. The sound is that bond breaking, and the force that it takes to make this happen is perhaps ten times what it would take to move a bullet that has not "cold welded" to the case neck. It is one of those things that I believe have to be experienced to understand, and to understand to come up with an explanation. Lots of experienced shooter/relaoders who have not had occasion to change the seating depth of long loaded rounds, have not experience this phenomenon. On the other hand, quite a few have.
https://www.google.com/search?q=cold+welding+of+case+necks&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a