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

[Dans40X]

A load cell in use seating projectiles a week in advance & then seated to depth 12-24hrs prior to shooting will eliminate all doubt, as a bore scope does to verify barrel abnormalities & cleaning.

Lots of variables!!

It's the only reason that I coat projectiles compared to running them naked.

A VLD/tapered reamer to remove burrs pushed into case mouths w/ 45deg inside case mouth de-burring tools is a must also.

 

[jlow]

Perhaps painting the inside of case necks with nitrocellulose lacquer, an letting it dry before seating bullets? If it would survive bullet seating, with perhaps a thin coating of wax on the bullet......Just a thought

I think the fact is it actually should takes a lot of prep to get the bullet and neck clean enough for cold welding to happen since it is a molecular thing and so if you interrupt the molecule/molecule interaction with a minute amount of contaminant, cold welding should not happen.

With that in mind, even an ultra thin coating of wax that completely covers the bullet should stop any cold welding dead in its tracks.

 

[TC260]

Welcome to the forum,...from your first two posts you look like you will be a real asset to this forum and it's members

Thanks Wayne. I've been reading the board for a few weeks and believe me when I tell you, you guys are waaaaay beyond my level in shooting and reloading knowledge. I've just had some chemistry and materials classes in college so I'm not an expert by any stretch.

This is a tough question. Seems like every explanation has flies in the ointment. One thing that does seem relatively consistent though is clean necks. Whatever the phenomenon is that's causing the two to stick together it seems to be exacerbated by bare metal contact.

 

[TC260]

I think the fact is it actually should takes a lot of prep to get the bullet and neck clean enough for cold welding to happen since it is a molecular thing and so if you interrupt the molecule/molecule interaction with a minute amount of contaminant, cold welding should not happen.

I agree with you. That seems to be the big monkey wrench in the cold welding explanation.

 

[BoydAllen]

Perhaps it is as simple as this. Bullets have jackets that already come with a thin layer of oxidation that probably is scratched minutely in seating, exposing thin lines of un-oxidized jacket, and if you clean a case neck to bare metal, even if it is only in spots, and then seat the bullet, the oxide layer that forms on the inside of the necks, and on those areas of the bullet where clean copper was exposed, form a single layer that is common to the bullet and case, and is equally attached to both. This is what a friend, who is a materials engineer came up with, and I think that he may have the answer. Both the brass and gilding metal are copper alloys, so the major component of their oxidized surfaces is copper oxide (which comes in two forms, one of which is red).

In the case of moly coated bullets there may be something else going on. Perhaps the copper, oxygen, and molybdenum disulphide form a compound, that has a strong chemical bond to the case and the moly coating on the bullet. In either case, something as simple as wax, and/or a layer of powder fouling can keep this common layer from forming. Factory cases do not turn the color of used brass until they have been handled in some way and/or heated by firing, this would tend to make me think that there is something on their surfaces that may help to prevent what we call cold welding, and bullets may have something similar, so that they don't become "ugly" (heavily and/or unevenly oxidized) in the box. Opinions?

 

[queen_stick]

interesting thread here,

Here's an idea that I didn't see mentioned (or I missed it).

Who wears gloves when they're handling their bullets?

I don't, and if I touch a bullet, then leave it on the bench (or put it back in the box) the next day, there's corrosion on the bullet that matches the pattern of my finger print. (sometimes it takes longer than a day to show up, but it will show up). SO, maybe the oil/salt/ on our hands is creating a chemical bond between the jacket and the case neck as the jacket begins to corrode as a result of our filthy fingers. We know for a fact that chemical reactions create a very solid "weld" with bullet jackets. The lead cores are purposely corroded prior to swaging, which 'mates' the lead core to the jacket, in a permanent manner. Perhaps the same chemical bond is occurring between the jacket and the case neck due to some sort of contamination.

could be WAY off with this theory too...

Walt

 

[bozo699]

interesting thread here,

Here's an idea that I didn't see mentioned (or I missed it).

Who wears gloves when they're handling their bullets?

I don't, and if I touch a bullet, then leave it on the bench (or put it back in the box) the next day, there's corrosion on the bullet that matches the pattern of my finger print. (sometimes it takes longer than a day to show up, but it will show up). SO, maybe the oil/salt/ on our hands is creating a chemical bond between the jacket and the case neck as the jacket begins to corrode as a result of our filthy fingers. We know for a fact that chemical reactions create a very solid "weld" with bullet jackets. The lead cores are purposely corroded prior to swaging, which 'mates' the lead core to the jacket, in a permanent manner. Perhaps the same chemical bond is occurring between the jacket and the case neck due to some sort of contamination.

could be WAY off with this theory too...

Walt

Sounds viable to me Walt. do a experiment what could it hurt
Wayne.

 

[jlow]

Perhaps it is as simple as this. Bullets have jackets that already come with a thin layer of oxidation that probably is scratched minutely in seating, exposing thin lines of un-oxidized jacket, and if you clean a case neck to bare metal, even if it is only in spots, and then seat the bullet, the oxide layer that forms on the inside of the necks, and on those areas of the bullet where clean copper was exposed, form a single layer that is common to the bullet and case, and is equally attached to both. This is what a friend, who is a materials engineer came up with, and I think that he may have the answer. Both the brass and gilding metal are copper alloys, so the major component of their oxidized surfaces is copper oxide (which comes in two forms, one of which is red).

I think you have it BoydAllen. When you get cold welding between bullet and case, I think it is only with very small surfaces as you say that are clean. Even a significant welding of say 10% of the surfaces would make it impossible to break with a seating die without collapsing the shoulders. However, even though it is a small % of the surface, the strength is still very significant and so would very likely affect the pressure required to release the bullet i.e. like having inconsistent neck tension and so not so good for accuracy/precision.

 

[BoydAllen]

It would seem that none of this bodes well for the stainless pins and tumbler crowd, unless their liquid had something in it to form a protective film on clean cases. Perhaps this thread will make some view powder fouling in case necks in a different light. Todd Kindler ( The Woodchuck Den) sells a water and wax based bullet coating that is applied by dipping. With years of his own, and customers' experience, he claims longer barrel life and less fouling. Perhaps it is time to try some. It is inexpensive. I think that Wayne has given us the basis for a test, unwaxed moly coated bullets, and necks freshly cleaned with steel wool on a bronze brush, or perhaps any oil and wax free bullet in a case neck cleaned the same way.

 

[bozo699]

It would seem that none of this bodes well for the stainless pins and tumbler crowd, unless their liquid had something in it to form a protective film on clean cases. Perhaps this thread will make some view powder fouling in case necks in a different light. Todd Kindler ( The Woodchuck Den) sells a water and wax based bullet coating that is applied by dipping. With years of his own, and customers' experience, he claims longer barrel life and less fouling. Perhaps it is time to try some. It is inexpensive. I think that Wayne has given us the basis for a test, unwaxed moly coated bullets, and necks freshly cleaned with steel wool on a bronze brush, or perhaps any oil and wax free bullet in a case neck cleaned the same way.

Now we are starting to get close to what I have been thinking.

 

[jlow]

I use SS-media and based on what I see, IMHO I don’t think it is a recipe for cold welding unless taken to the extreme. I clean my rifle brass for about 4 hours with the media and although the externals and primer pockets are very clean, the necks themselves are not. There is certainly no visible carbon on them but the inside of the necks are still tarnished which to me is fine. The reason for this is because the only rubbing action on the neck is with media that is already sitting in line with the case neck because of its limited dimensions.

This is the thing with life, anything taken to extremes usually causes trouble and I think SS-media is no different. I think unless someone cleans their brass for really extended periods (which I see no reason to do) or goes to the extreme of polishing the inside of their necks with stainless steel wool, there should not be a problem. This is especially true if you add a neck lubricant which would act also as a contaminant in this instance.

 

[gilream]

Boyd…In the fall 2010 I was set up at the range prior to hunting season and decided to shoot a couple of groups with the 30/06--150 grain Ballistic Tip hand loads that had been sitting in my safe for about 10 years. I fired the first shot and the chronograph read 3150. I scratched my head and fired another shot that read 3165. Since the normal velocity for these loads should be around 2980 I stopped and set them aside. At home using a hammer type bullet puller I took the remaining rounds apart. It was noticeably harder to get the bullet to fall out but I reweighed the powder, which was correct, and reseated the bullets. They showed normal velocities and accuracy when I fired them later the next week. This was very confusing to me at the time and I attributed the high velocity to a seating die improperly set up to crimp (which is unlikely but it’s all I could think of). I used a Lee collet die to resize the case necks originally and brushed the inside neck diameter out with a nylon brush. Now I am thinking that these Ballistic Tips could have possibly been “cold bonded” to the cases as described in this thread. Thanks for giving me a possible explanation for that freaky incident from 2010.

 

[Tozguy]

Thanks Boyd for opening up such a fascinating subject. Also, thanks to others who have provided links to some very good reading. Unfortunately I don’t have any personal test results on ammo ‘pop’ to contribute but here are some observations made over the years that might relate.

Wayne slipped in a comment on galling of ss barrels in ss actions which got me thinking, When expanding the necks on new brass it always impressed me how easily the brass would stick to the steel mandrel. Because the new brass only needed to be expanded by one or two thou., I tried to expand the necks without using lube. It only took a few cases before brass lumps started building up on the mandrel. Once a lump was started, it would build up very quickly. The brass mysteriously transferred to the steel in very localized spots. There were only 3 to 4 lumps of brass on the steel mandrel but they were raised and were very difficult to remove.

From this it appears that the brass ‘cold welded’ to the mandrel under little pressure. The brass to steel weld was as strong as the brass itself considering how easily the brass was 'given up' by the case. Brass build up on the mandrel also indicates significant brass to brass welding.

Then I applied some dry lube by dipping the necks in some No. 6 lead shot saturated with motor mica. The dry lube did not seem to stick very well to the new brass but I proceeded anyway. Brass transfer to the mandrel continued but at a slower rate. After that some moly engine assembly lube was applied to the inside of the necks using a Q-tip. This put an end to the ‘cold welding’ during neck expansion.

This left me wondering whether there would be evidence of ‘cold welding’ between case and bullet if we removed a ‘popping’ bullet from a case for inspection. It seems to me that ‘cold welding’ would leave evidence of metal transfer (pitting, galling, etc). Would the absence of metal transfer point to some kind of bonding by an intermediate layer (coating on the brass or bullet).?

Another indication of bonding would be the time factor. If the ‘popping’ only develops over time would this not indicate that it is due to bonding of some kind as opposed to ‘cold welding’ which is immediate?

Respectfully, MikeB

 

[jlow]

I can’t be sure but I think the galling and cold welding are two different things. I think galling comes from rubbing two surfaces together and it is the friction between two not 100% smooth surfaces that results in the transfer, a bit like how sand paper would remove wood from a 2x4 and how that would load up the sandpaper. This is why if you lubricate the mandrel, it would slip by the neck and not cause galling.

Cold welding on the other hand I think develops over time without additional force or movement. So say for example, if you seat a bullet in a case and the two surfaces were very clean and very smooth, the seating would be a smooth process and if you extracted the bullet immediately afterwards it would be a relatively easy process. However, if you let the two sit together, the cold fusion would slowly bond the two surfaces together and what you might find under ideal circumstances is an increase in effort to extract the bullet as a function of time. Not this bonding may be infinite i.e. it will get to a plateau and no further cold fusion would happen since all the available surfaces i.e. the high spots have bonded.

One could test this theory by putting together batches of 3 to 5 round bullet/case combo and using something like the K&M “Arbor press with force measurement and dial indicator” to seat each batch of bullet/case combo once 50 thousands deeper at different time after they were put together i.e. 1 min, 1 hour, 10 hours, 100 hours, 1000 hours. If there is no such thing as cold welding, the amount of force needed to seat the bullet will be similar and unchanging for all the batches. If cold welding exists, seating force will increase over time and perhaps plateauing over time.

I am no expert but this is how I would read and test it.

 

[queen_stick]

...

Another indication of bonding would be the time factor. If the ‘popping’ only develops over time would this not indicate that it is due to bonding of some kind as opposed to ‘cold welding’ which is immediate?

That's exactly what I was getting at.... my idea is that the 'film' on the bullet is coming from us touching the bullet. That film is the oil and whatnot from our hands, which later creates corrosion (chemical reaction) which bonds the two surfaces. Maybe the corrosion is so slight, that the bullets will appear clean to the naked eye.

I have no scientific data to base this on, but I feel this is a bonding issue (due to a chemical reaction), and NOT a 'cold weld' condition (pressure).

Wayne suggested testing this theory, and here's what I'm thinking about trying... Ultrasonic clean a few cases, seat some bullets that are cleaned, and only handled with gloves, and also seat a few bullets that I handle normally (no cleaning, and no gloves). A few weeks later, try to seat them deeper, and see if there's a difference in pressure required to "break the bullet loose" between the cleaned bullets and the 'regular' bullets. Only problem is, I don't have a k&M press with a stress gauge, so it would be based on feel if I did this.

I do have one question though... to get a bullet completely clean, what would you use to clean it with?

 

[jlow]

Yip, that is absolutely true. The problem with the experiment I suggested is that it would not be able to distinguish between a true cold welding and one where the bullet and case is held together by corrosion. I have been struggling with this since I first suggest it.

As for cleaning, the first thing you want to do is to remove any corrosion and oils that is on the surface, I would suggest SS media coupled with detergent/Lemishine which would dissolve/abrade both off (it is more effective than ultra sonics). The next part would be to remove any salt deposited from the liquid used to clean the brass/bullet. For this, I would suggest highly distilled water via a stepwise dilution process.

For the experiment, I would suggest a number of different conditions. One would be the completely clean stuff. Another could be cleaned bullet/case that has been doped with salt that would encourage corrosion. Still another could be cleaned bullet/case that is protected against cold welding/corrosion using a wax coating like Imperial.

Apart from the seating pressure, a more direct approach would be to section the bullet/case combo without breaking the bond, section specifically the bonded area and do electron microscopy and elemental analysis which will give you an absolutely clear proof of what is holding the two together. Very expensive and high tech but that is life.

Yea, I too don’t have the K&M tool but have been tempted. The only down side of the tool is that it appears to not allow you to use regular seating dies like the Redding micrometer compettion seating die that I like to use….

 

[300 RUM]

Like I said before, If any one has a round that posses this phenomena send it to me, I can examine it in my lab (microscope, spectrum analyzer etc) need I say more.

Contact me off line

 

[jlow]

Guess we are looking for someone who is interested in doing the experiment, have the right equipment to measure the seating pressure, and can team up with 300 RUM.

 

[johara1]

I can not understand the cold welding , number one all factory ammo would be near useless because you could not depend on it to shoot a group. With cold welding in some of the rounds and not the others. Second you load rounds for hunting and don't them for years and go back and they still shoot small groups. To pull or reseat the bullets to find this,i don't think so but uniform neck tension is so important it would show up on any ammo when shooting groups or sighting in. In over a 100 yrs. loading between a friend, we have never seen it......jim

 

[jlow]

I can not understand the cold welding , number one all factory ammo would be near useless because you could not depend on it to shoot a group. With cold welding in some of the rounds and not the others. Second you load rounds for hunting and don't them for years and go back and they still shoot small groups. To pull or reseat the bullets to find this,i don't think so but uniform neck tension is so important it would show up on any ammo when shooting groups or sighting in. In over a 100 yrs. loading between a friend, we have never seen it......jim

I think the key to your question is that despite what one might think it is actually HARD to get cold welding. If you read this link I posted before which I will repost here:

http://www.coldpressurewelding.com/cms/index.php?option=com_content&view=article&id=92&Itemid=2&lang=en

This is the explanation and the key statement in red:

“Therefore, if two metallic surfaces are brought together with only a few angstroms separation, there being 300 million angstroms to one centimeter, interaction between the free electrons and ionized atoms can occur. This will eliminate the potential barrier, allowing the electron cloud to become common. This, in turn, results in a bond and therefore a weld.

A simpler way of explaining this rather awesome process is that if two surfaces are put together, both being anatomically clean and anatomically flatwhen considered on an atomic scale, a bond is effected equal to that of the parent material.”

As you can see, it requires the surface to be “anatomically clean”, any contaminants will screw things up. Knowing this, any ammunition manufacturer can dope the surface with another substance to foil cold welding.