Cold welding, bullet to case neck bonding

[Spitpatch]

Concern level ZERO.

No charge for this service, drive safely.

 

[Local Loader]

I havent read of anyone using a sealant (Im aware that some milsurp ammo uses it).

Most reloaders clean their brass so I would think most handloads the metals are free of conaminates between them. Its an obscure topic though and so far the consensus here is nobodys experienced this phenomenon, yet.

So most metals start to develop an oxidation layer after cleaning or cutting which is also considered a contaminate. That oxidation is what normally prevents them from cold welding. For reloading I wouldn't worry about it as the chances are likely less than 0.0001% of it happening, unless you load in a vacuum chamber.

 

[P7M13]

Just one more thing for anal-retentive reloaders to lose their $h1t about....
I pulled ~150 hand loaded rounds that had been loaded in the '80s. Maybe 1/4 had what I would call "galvanic bonding". They were harder to pull, but not one required enough clamp force to damage the bullet

 

[Certaindeaf]

Mike Irwin's post touches on the cupronickle subject..

Cold weld ? - The Firing Line Forums

Cold weld ? Handloading, Reloading, and Bullet Casting

thefiringline.com

 

[Koda]

Mike Irwin's post touches on the cupronickle subject..

Cold weld ? - The Firing Line Forums

Cold weld ? Handloading, Reloading, and Bullet Casting

thefiringline.com

more guns and ammo history in gun forums than one can shake a stick at...

 

[Greenbug]

It is more of a topic recently with the widespread use of SS pins and wet tumbling that really clean all the carbon off the inside of the case necks. Seat a clean bullet into a clean (no carbon residue) case neck and the two dissimilar metals "cold weld" over a period of time. I have experienced this and measured it's negative effect on standard deviation in velocity and downrange consistency. It is a thing, but most average shooters will likely never notice.

 

[Koda]

It is more of a topic recently with the widespread use of SS pins and wet tumbling that really clean all the carbon off the inside of the case necks. Seat a clean bullet into a clean (no carbon residue) case neck and the two dissimilar metals "cold weld" over a period of time. I have experienced this and measured it's negative effect on standard deviation in velocity and downrange consistency. It is a thing, but most average shooters will likely never notice.

So is the cleanliness of the brass the root cause of it?
If it comes down to that then it can be solved with the handloading process except maybe with new virgin brass.

 

[Greenbug]

So is the cleanliness of the brass the root cause of it?
If it comes down to that then it can be solved with the handloading process except maybe with new virgin brass.

Seems to be the main contributing factor in my opinion, but I am not a scientist or metal guy, heck I never even stayed at a Holliday Inn. The clean brass inside the case neck interacts with the copper jacket on the bullet over time and "bonds" causing a bigger build up of pressure in the case before the bullet breaks the "weld" and starts down the bore during ignition.

 

[Koda]

Seems to be the main contributing factor in my opinion, but I am not a scientist or metal guy, heck I never even stayed at a Holliday Inn. The clean brass inside the case neck interacts with the copper jacket on the bullet over time and "bonds" causing a bigger build up of pressure in the case before the bullet breaks the "weld" and starts down the bore during ignition.

this was my suspicion on this so its good to hear the same opinion. Im not a scientist either but can roll with this. Ive got some rounds I loaded this week in virgin brass but I might not be able to shoot them for a few months but I think they will be ok as the load isnt near pressure. As for reloaded cases my sonic clean process doesnt get the inside very clean at all so I probably dont need to worry about this after once fired.
I think Im good with this conclusion.

 

[dangerranger60]

It is more of a topic recently with the widespread use of SS pins and wet tumbling that really clean all the carbon off the inside of the case necks. Seat a clean bullet into a clean (no carbon residue) case neck and the two dissimilar metals "cold weld" over a period of time. I have experienced this and measured it's negative effect on standard deviation in velocity and downrange consistency. It is a thing, but most average shooters will likely never notice.

I don't think that's how cold-welding works. two very clean, "Thin" metals are pressed together to make them bond. In order to keep them clean enough this is done in a vacuum. and the bond is instant, not over time. What you are describing is corrosion. or the chemical reaction of dissimilar metals. DR

 

[Koda]

I don't think that's how cold-welding works. two very clean, "Thin" metals are pressed together to make them bond. In order to keep them clean enough this is done in a vacuum. and the bond is instant, not over time. What you are describing is corrosion. or the chemical reaction of dissimilar metals. DR

this is probably correct, I do suspect "cold weld" wasnt the literal process thats happening. The net effect is some kind of bonding and thus increase in neck tension increasing pressure.

 

[Greenbug]

I don't think that's how cold-welding works. two very clean, "Thin" metals are pressed together to make them bond. In order to keep them clean enough this is done in a vacuum. and the bond is instant, not over time. What you are describing is corrosion. or the chemical reaction of dissimilar metals. DR

Corrosion over time or the reaction of dissimilar metals are probably more accurate descriptions of what is theoretically happening in this situation. Just trying to convey my thoughts on what I think is happening when people mention "cold welding" as it currently is being discussed on the interwebs in regards to handloading ammunition.

 

[P7M13]

I used to work designing metallurgy heat treating equipment just out of college.
I see four issues here.
1. When dissimilar metals are bound together, changes in temperature cause electrons to flow between the metals. This is the Seebeck effect. Over time this will generate bonding structures between the two metals. Time as in many decades.
2. The metal content of the bullet jacket and the cartridge brass composition. Some cartridge brass contains tin, which increases salt corrosion resistance. Tin, copper & heat produces a molecular bond that we know as soldering. At room temperature, it will happen, but also a slow process
3. The most likely scenario is the sulfur in the air and in the oils in our hands, causing the brass and bullet surfaces to corrode together over time.
4. Decomposition of powder inside the case can yield compounds that would readily corrode/bind the brass and bullet together.

Controls that can help you avoid this:
1. Store your loaded rounds in a controlled temperature & humidity location, avoiding temp swings, etc.
2. Store your bullets and clean brass in a controlled atmosphere, i.e. not exposed to open air. Or load the brass promptly after cleaning.
3. Apply a film on the inside of the case necks, such as the graphite mentioned. Caution - some materials may react with the gunpowder or induce corrosion. I use Meguires car wash/wax when I tumble and am happy with the wax film residue on the brass. I've dabbled with graphite and noted the application methods I tried delivered spotty results.
4. Lastly, experiment with your loads and determine the effects so you understand the limits of your controls. One man's controlled system is another man's definition of chaos.

I believe @Greenbug noted that the effect was noticable among competition shooters, but that again comes down to what accuracy you are hoping to achieve and what your equipment and skill can deliver.

 

[Koda]

3. Apply a film on the inside of the case necks, such as the graphite mentioned. Caution - some materials may react with the gunpowder or induce corrosion. I use Meguires car wash/wax when I tumble and am happy with the wax film residue on the brass. I've dabbled with graphite and noted the application methods I tried delivered spotty results.

I would consider adding a step like this to my process if I knew it wouldn't change my current recipe?

Ive put work into the load development process and just want to be done with that part. I handload for hunting, so I plan to have a box of ammo on the shelf at all times for each rifle I hunt with... so there is potential that some ammo wont get shot up for months or longer.
What weve learned here is that it can happen, just not certain how consistent it is. I dont mind mitigating a rare possibility as long as it doesnt change my current results?

 

[DizzyJ]

As mentioned above, I've often wondered if it's caused by the oils/salts on our fingers/hands. This is just one reason why I wear gloves when handling bullets and brass.

I know of one hand loader who seats long before the match then final seats immediately prior to shooting them.

 

[gmerkt]

In my case.....the bullets weren't "welded".
More like, I had an issue with case necks split (.308W reloads). Because, I don't/didn't anneal the brass and the cases had been used many, many times before being stored.

For the Average Joe reloader, I'd say the above is a lot more likely to be a worry over time than any issue with a fusing of the two surfaces together.

Over the years, I've seen decades-old ammo where the bullets had been fused into the case mouth but these were a result of corrosion.

I've made it a practice not to finish every reloaded case in sight just because it could be done. I'd do all the case prep (which is the most choresome part of reloading), then box up and store the finished cases. When I'd anticipate need, I'd get out some cases, then finish the task. Priming, charging and bullet seating all take a lot less time than proper case prep. That way, I wouldn't have reloaded ammo sitting around for years. If you're going to have reloading stuff sit around for any length of time, my feeling is it's best to let it remain as components rather than as finished ammo. Yes, it's wise to keep enough finished ammo on hand to fend off an army of zombies. Even in that eventuality, there are limits as to what you need on hand for immediate use.

 

[dangerranger60]

I would consider adding a step like this to my process if I knew it wouldn't change my current recipe?

Ive put work into the load development process and just want to be done with that part. I handload for hunting, so I plan to have a box of ammo on the shelf at all times for each rifle I hunt with... so there is potential that some ammo wont get shot up for months or longer.
What weve learned here is that it can happen, just not certain how consistent it is. I dont mind mitigating a rare possibility as long as it doesnt change my current results?

I also as part of my brass prep add a little wax. It keeps my processed brass clean and polished for years. From the description of cold welding it would also keep the metals from bonding. And keep them from corroding. A win win all the way around. DR

 

[dangerranger60]

For the Average Joe reloader, I'd say the above is a lot more likely to be a worry over time than any issue with a fusing of the two surfaces together.

Over the years, I've seen decades-old ammo where the bullets had been fused into the case mouth but these were a result of corrosion.

I've made it a practice not to finish every reloaded case in sight just because it could be done. I'd do all the case prep (which is the most choresome part of reloading), then box up and store the finished cases. When I'd anticipate need, I'd get out some cases, then finish the task. Priming, charging and bullet seating all take a lot less time than proper case prep. That way, I wouldn't have reloaded ammo sitting around for years. If you're going to have reloading stuff sit around for any length of time, my feeling is it's best to let it remain as components rather than as finished ammo. Yes, it's wise to keep enough finished ammo on hand to fend off an army of zombies. Even in that eventuality, there are limits as to what you need on hand for immediate use.

I'm another that processes large batches of brass and then store it in airtight containers. I load in batches I'm likely to use in a year or two. DR

 

[gmerkt]

Re. the military loads that seal a bullet in place with "asphaltum" (as the reloading books call it). We can't see what's going on in there at the time of ignition, but my surmise is that a pico second after the powder goes off, the heat generated by this process melts then burns off the sealant. Hence there is no pressure build-up resulting purely from the sealed bullet.

 

[Ziggy44]

Cold "welding", bullet to case neck bonding. I came upon this subject in another forum but want to hear opinions from those I know longer here. What happens is handloads somehow bond to the case neck over time, increasing chamber pressure when firing. A common solution is to lube the bullet in graphite before seating.

A quick web search shows only a few discussions, so this is indeed a topic if somewhat obscure. I'm trying to judge just how much of a concern it is?


reloading photo for attention:
View attachment 1487754

All lake city 5.56 rounds have the projectile sealed into the neck with asphalt.
Pretty common with military ammo to enamel the primer and case to projectile rim.