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I Want To Thank The Sun

918v

918v

Range Physic
Full Member
Minuteman
Jul 15, 2007
8,246
6,648
Miserable CA
#1
Last week was real hot, like 110 degrees all week. So I didn’t go to the range. I had loaded up some ammo and just let it sit there, admiring it yet hating it at the same time. You see, this revolver I have has been giving me fits. I could never get the kind of accuracy out of it that I wanted. Which brings me to this phenomenon:

Do you remember a few years back we had a discussion about cold welding? People made arguments for and against the existence of the phenomenon we call cold welding. I know it exists because it is harder to pull bullets from ammo that has been sitting around vs ammo you just loaded. A suggestion was made to push the bullet deeper into the case before trying to pull it. This usually results in a small pop sensation which breaks the “weld”.

This has to affect internal ballistics somehow and it did in two ways: velocity and accuracy. The velocity of this ammo that had sat for a week went up 30-40 FPS and accuracy improved by 70%.

I am very happy with the revolver now but I want to study the phenomenon further. My question to you all is how long do you wait before shooting the ammo you loaded and have you even considered what is happening to neck tension over time?

I have a feeling the neck continues to tighten its grip around the bullet for a period of time until it sorta stabilizes. Someone on the internet said it’s 24hrs but I think it might be longer. This may affect accuracy or not depending on the application but in the case of my revolver it definitely does.
 
#2
918v said:
Last week was real hot, like 110 degrees all week. So I didn’t go to the range. I had loaded up some ammo and just let it sit there, admiring it yet hating it at the same time. You see, this revolver I have has been giving me fits. I could never get the kind of accuracy out of it that I wanted. Which brings me to this phenomenon:

Do you remember a few years back we had a discussion about cold welding? People made arguments for and against the existence of the phenomenon we call cold welding. I know it exists because it is harder to pull bullets from ammo that has been sitting around vs ammo you just loaded. A suggestion was made to push the bullet deeper into the case before trying to pull it. This usually results in a small pop sensation which breaks the “weld”.

This has to affect internal ballistics somehow and it did in two ways: velocity and accuracy. The velocity of this ammo that had sat for a week went up 30-40 FPS and accuracy improved by 70%.

I am very happy with the revolver now but I want to study the phenomenon further. My question to you all is how long do you wait before shooting the ammo you loaded and have you even considered what is happening to neck tension over time?

I have a feeling the neck continues to tighten its grip around the bullet for a period of time until it sorta stabilizes. Someone on the internet said it’s 24hrs but I think it might be longer. This may affect accuracy or not depending on the application but in the case of my revolver it definitely does.
Click to expand...
Since I have no experience in reloading for pistols, I can't address that issue for them. But, I have taken notes and tested .308 brass on this issue. How much and how fast cold welding depends on what's on the interior neck surface or if nothing at all (like the neck has been cleaned sparkling clean).

When the necks are really clean, the cold welding happens pretty easy over a couple weeks. I did not experience any of it in just a few days with the clean necks.

With the carbon deposits from firing left in the neck (no lube), the cold welding took a few months before I could detect anything. The way I tested them was simply by trying to seat them deeper. If they seated seated more without any unusual effort and abrupt pop, I concluded there was no cold welding going on.

When I clean my brass with rice in a vibrator tumbler, the rice leaves a hint of a coating I can only detect by how it's easier to seat a bullet. That coating along with what's left of the carbon deposits, keeps the cold welding from occurring for many months. At least it does in this dry climate of Arizona where I live. I suspect in a more humid climate, the results would be different.

What really works best for me now, where I never have any cold welding (like I've gone 6+ months on some loads), is the cleaning with rice to remove the Imperial Sizing Die Wax off after sizing, which leave a hint of the wax in the neck on top of what's left of the carbon deposit. I've not detected any change in seating resistance over time this way.

Note: It's not unusual for me to load long before going to the range and sometime weeks can go by before I shoot the load. But it is typical of me to load the day before or just a few days before I go to the range to shoot.
 
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#3
I had some 308 ammo I let sit for a couple years to test this. Unfortunately when I started checking with a seating die. I didn't find any that popped loose. I had some 22-250 that were locked in tight in a few months.
 
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#4
I cleaned these ultrasonically, dried them, and followed up with 20min in a tumbler with corncob and Nufinish.

I’ve been loading the rounds the day before and shooting them in the morning. I was getting ok accuracy but the groups had fliers.

The week-old ammo shot amazing. I dunno what happened other than sitting around. The process was the same. The humidity was the same. The ambient temperature was the same. Everything was the same.

If it’s not cold welding then maybe it should be renamed to neck tension settling?
 
#6
918v said:
I cleaned these ultrasonically, dried them, and followed up with 20min in a tumbler with corncob and Nufinish.

I’ve been loading the rounds the day before and shooting them in the morning. I was getting ok accuracy but the groups had fliers.

The week-old ammo shot amazing. I dunno what happened other than sitting around. The process was the same. The humidity was the same. The ambient temperature was the same. Everything was the same.

If it’s not cold welding then maybe it should be renamed to neck tension settling?
Click to expand...
I think that's a good point about "settling" of the neck tension. It's not something I've figured out how to test, but having worked with various sheet metal alloys I don't see that there's really but a very small if any effect with most neck tensions being used. If the neck's a really tight fit, then that phenomenon is very likely an issue. For me, with neck tensions I use of .0015 - .002 in freshly annealed necks, I just don't see how there be any "settling". More likely, exposure to a humid environment leaking through the necks can be a much bigger issue since the necks aren't exactly air tight. . .especially during any substantial fluctuation in temperatures. 🤷‍♂️
 
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#7
straightshooter1 said:
For me, with neck tensions is use of .0015 - .002 in freshly annealed necks, I just don't see how there be any "settling".
Click to expand...
Wouldn't it be more likely that sized necks "relax" and lose some of their grip?

Increasing tension would require constriction... without any additional mechanical input or massive temperature changes, I don't see how that could occur
 
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#8
straightshooter1 said:
I think that's a good point about "settling" of the neck tension. It's not something I've figured out how to test, but having worked with various sheet metal alloys I don't see that there's really but a very small if any effect with most neck tensions being used. If the neck's a really tight fit, then that phenomenon is very likely an issue. For me, with neck tensions I use of .0015 - .002 in freshly annealed necks, I just don't see how there be any "settling". More likely, exposure to a humid environment leaking through the necks can be a much bigger issue since the necks aren't exactly air tight. . .especially during any substantial fluctuation in temperatures. 🤷‍♂️
Click to expand...

Maybe hardness affects it as well. The harder the neck the more it springs back.

I was using 1x Remington brass sized in a Redding dual carbide die which is unique in that it produces a bottle necked case out of a straight wall case (the body portion is larger in diameter than the neck portion) after seating the round is once again straight walled.

Revolvers are kinetic bullet pullers. If brass continues to tighten around the bullet over time, maybe this stops bullets from pulling out under recoil? But if that’s the mechanism producing accuracy then maybe I should just add a heavier roll crimp?
 
#9
Glue them in. "Chemical crimp"

25 years ago I was playing around with the 50AE round in a revolver, trying to get it to do things it really wasn't meant to. (shoot 400+ grain bullets above 1300fps with the crappy tapper crimp while maintaining headspace) Tried a few things, custom made "stake crimping" tool for one. But I couldn't stop wondering about crazy gluing the bullets into the case. I thought if I keep it consistent as possible and work up, it should be safe. I chickened out mostly because I didn't wan to start over and "work up".


Metals like brass and lead age harden, but it can't be happening that fast. More likely you're seeing a little tiny bit of spring back of the bullet after seating/crimping. Next question might be why is that helping? Is it a crimp thing? Or a bullet/throat/barrel size relationship thing? (though it shouldn't be springing back THAT much either)
 
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#13
918v said:
Is galvanic corrosion visible if you were to disassemble the ammo? Or would it look like galling?
Click to expand...
On the 22-250s I pulled down you could see some white powder dust that looked very much like galvanic corristion. They were almost denfinelty stuck and not just gripped harder. It took a fair amount of force to break them loose in my rockchucker with a seating die.
 
#16
supercorndogs said:
On the 22-250s I pulled down you could see some white powder dust that looked very much like galvanic corristion. They were almost denfinelty stuck and not just gripped harder. It took a fair amount of force to break them loose in my rockchucker with a seating die.
Click to expand...

I haven’t had that yet. I wonder if it’s moisture related. Probably is.
 
#17
R_A_W said:
Wouldn't it be more likely that sized necks "relax" and lose some of their grip?

Increasing tension would require constriction... without any additional mechanical input or massive temperature changes, I don't see how that could occur
Click to expand...
I'm thinking that just as there's springback after sizing, if a bullet is seated before this springback can occur, then there may be a small amount of additional tension added is the same way. If the brass has already fully sprung back before sizing, then there's no additional force being generated after seating. The only additional force I ever seen is between two dissimilar metals where there's some growth of the galvanic corrosion between the two surfaces.

For the necks to "relax" and lose some grip, I think would take a great deal of time. I seem to recall some WWI ammo found in an attack in Germany that still held together just fine. But I don't now if that might have been due to some galvanic corrosion adhesion or expansion. 🤷‍♂️
 
#20
straightshooter1 said:
I'm thinking that just as there's springback after sizing, if a bullet is seated before this springback can occur, then there may be a small amount of additional tension added is the same way. If the brass has already fully sprung back before sizing, then there's no additional force being generated after seating. The only additional force I ever seen is between two dissimilar metals where there's some growth of the galvanic corrosion between the two surfaces.

For the necks to "relax" and lose some grip, I think would take a great deal of time. I seem to recall some WWI ammo found in an attack in Germany that still held together just fine. But I don't now if that might have been due to some galvanic corrosion adhesion or expansion. 🤷‍♂️
Click to expand...

The direction of springback is important. And the amount of sizing is important as well.

Cases that went through a standard FL sizing die have necks that spring back in the direction of the bullet. Cases that were sized just barely using a bushing die will spring back away from the bullet.

In my case the brass is definitely springing back toward the bullet that’s why I think the grip is getting tighter over time.
 
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#23
918v said:
The direction of springback is important. And the amount of sizing is important as well.

Cases that went through a standard FL sizing die have necks that spring back in the direction of the bullet. Cases that were sized just barely using a bushing die will spring back away from the bullet.

In my case the brass is definitely springing back toward the bullet that’s why I think the grip is getting tighter over time.
Click to expand...
Likewise, mine springs back towards the bullet since I use an expander mandrel to set the neck tension. Though I seldom seat bullets within a 24 hr period after sizing.
 
#24
918v said:
Did you use the same primers for your 308 and 22-250 loads? I’m wondering if something in the primer residue might have reacted with the case lube.
Click to expand...
Cci250s in both but I had them from three diffrent vintages. I had 5k I think from the 80s and 5k I think from the 90s I traded a trigger for. And 5k from current (at the time) production.
 
#25
At great risk of bruising my ego, I'll offer my 2 cents on the subject.

I think part of the phenomena is static vs dynamic Friction. Generally, the coefficient of dynamic (moving) friction (D CoF) is less than that of the static (not moving) coefficient of friction (S CoF). If you are measuring bullet seating force, it's the dynamic friction force being measured. When pulling/re-seating a bullet, you must overcome the greater static friction force, after which the dynamic lesser friction force kicks in. This would mimic a spring back / neck tightening condition. For most materials, the S CoF is about 20% to 50% greater than the D CoF. It also seems that the disparity between the two becomes greater if the surface is lubricated. I couldn't find any good coefficient data for a copper/brass interface in my limited searching, but it has got to be out there. May be a thing, may not.

Also, by re-seating the bullet further in, besides overcoming the greater static friction force, you must also overcome the constriction of the neck where it is being expanded by the bullet. So re-seating a bullet would require a larger force than when it was seated. I don't know of anybody measuring the force required to pull (as opposed to re-seating) a bullet, or what apparatus could be used. So having data on this is probably limited. My guess is the force to pull a bullet would be closer to just the static friction force.

As far as galvanic corrosion, I don't generally think this is a cause. Copper (bullet, anodic index = 0.35) and brass (case, anodic index = 0.40) are very close together on the "ANODIC INDEX" ( https://www.engineersedge.com/galvanic_capatability.htm ). The difference in the ANODIC INDICES = 0.05 (0.40-0.35 = 0.05). According to that web site, a difference of 0.15 is suitable for harsh environments. Therefore, ammunition would need to be stored in a fairly severe environment to see the effects of galvanic corrosion between the jacketed bullet and case. That's not to say corrosion won't take place between the bullet and case, but not so much due to galvanic action/dissimilar metals. Also, the inside of the necks usually are not cleaned to the point of removing the oxide (tarnish), which lessens the conductivity and galvanic corrosion potential. Lubing the neck would probably also lessen the conductivity (depending on the lubricant). In my mind, relying on rice/walnut/corn cob dust as a lubricant may be iffy. These dusts attract moisture and may enhance corrosion (tarnishing) on each of the mating surfaces, but not by galvanic action. It would be interesting to test these against a petroleum based lube/wax.

For a number of years I have been tumbling my brass in walnut shells that I add a cap of Nushine and a good quality carnuba wax. I also throw in a capful of mineral spirits which keeps the dust down. My belief is that the wax provides adequate neck lubrication. I'm satisfied with the consistent seating forces I get, or as best as I can tell with a KM arbor press with a dial gauge/belleville washer set up.

Cold Welding: Not real familiar with it, but seems you have to have super clean (0% oxides/tarnish) and highly polished mating surfaces under a lot of pressure to make this happen. One reference I read said the pressure needs to cause more than a 35% deformation in the mating surfaces for cold welding to occur. There maybe some of this, but to me, seems unlikely.

I agree with R_A_W regarding the tension not increasing with time. This would require additional energy input to cause this. Maybe there is some stored (potential) energy within the grain structure that would cause this, but my it's my understanding that changing the grain structure (cold working) and spring back is pretty much an instantaneous thing. I refer back to the static vs dynamic friction conjecture.

All of this is just qualitative stuff and don't have any meaningful data on it. So there you go.
 
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#26
Hula Popper said:
At great risk of bruising my ego, I'll offer my 2 cents on the subject.

I think part of the phenomena is static vs dynamic Friction. Generally, the coefficient of dynamic (moving) friction (D CoF) is less than that of the static (not moving) coefficient of friction (S CoF). If you are measuring bullet seating force, it's the dynamic friction force being measured. When pulling/re-seating a bullet, you must overcome the greater static friction force, after which the dynamic lesser friction force kicks in. This would mimic a spring back / neck tightening condition. For most materials, the S CoF is about 20% to 50% greater than the D CoF. It also seems that the disparity between the two becomes greater if the surface is lubricated. I couldn't find any good coefficient data for a copper/brass interface in my limited searching, but it has got to be out there. May be a thing, may not.

Also, by re-seating the bullet further in, besides overcoming the greater static friction force, you must also overcome the constriction of the neck where it is being expanded by the bullet. So re-seating a bullet would require a larger force than when it was seated. I don't know of anybody measuring the force required to pull (as opposed to re-seating) a bullet, or what apparatus could be used. So having data on this is probably limited. My guess is the force to pull a bullet would be closer to just the static friction force.

As far as galvanic corrosion, I don't generally think this is a cause. Copper (bullet, anodic index = 0.35) and brass (case, anodic index = 0.40) are very close together on the "ANODIC INDEX" ( https://www.engineersedge.com/galvanic_capatability.htm ). The difference in the ANODIC INDICES = 0.05 (0.40-0.35 = 0.05). According to that web site, a difference of 0.15 is suitable for harsh environments. Therefore, ammunition would need to be stored in a fairly severe environment to see the effects of galvanic corrosion between the jacketed bullet and case. That's not to say corrosion won't take place between the bullet and case, but not so much due to galvanic action/dissimilar metals. Also, the inside of the necks usually are not cleaned to the point of removing the oxide (tarnish), which lessens the conductivity and galvanic corrosion potential. Lubing the neck would probably also lessen the conductivity (depending on the lubricant). In my mind, relying on rice/walnut/corn cob dust as a lubricant may be iffy. These dusts attract moisture and may enhance corrosion (tarnishing) on each of the mating surfaces, but not by galvanic action. It would be interesting to test these against a petroleum based lube/wax.

For a number of years I have been tumbling my brass in walnut shells that I add a cap of Nushine and a good quality carnuba wax. I also throw in a capful of mineral spirits which keeps the dust down. My belief is that the wax provides adequate neck lubrication. I'm satisfied with the consistent seating forces I get, or as best as I can tell with a KM arbor press with a dial gauge/belleville washer set up.

Cold Welding: Not real familiar with it, but seems you have to have super clean (0% oxides/tarnish) and highly polished mating surfaces under a lot of pressure to make this happen. One reference I read said the pressure needs to cause more than a 35% deformation in the mating surfaces for cold welding to occur. There maybe some of this, but to me, seems unlikely.

I agree with R_A_W regarding the tension not increasing with time. This would require additional energy input to cause this. Maybe there is some stored (potential) energy within the grain structure that would cause this, but my it's my understanding that changing the grain structure (cold working) and spring back is pretty much an instantaneous thing. I refer back to the static vs dynamic friction conjecture.

All of this is just qualitative stuff and don't have any meaningful data on it. So there you go.
Click to expand...
It's my understanding that the military used to use a wax coating (either on the neck or bullet) as a measure to keep moisture from entering the case. I wonder how much of a certain kind of wax it takes to do that??? Since I use Imperial Sizing Die Wax for sizing, then dry tumble with rice leaving a hint of that wax on the surfaces, there may be some protection in the neck and primer pocket. Though I doubt it's enough to really help seal the case. And note that the rice has almost no dust and leaves virtually no dust behind, especially when used to remove the sizing wax.

There is an instantaneous springback, but it's not all done instantaneously, especially as the brass becomes more and more work hardened. This is easily testable. Like I measured the necks OD of sized brass after sizing and again 24hrs later and saw as much as .001 difference on various .308 cases with various neck thicknesses. On properly annealed brass, it's not anywhere near that much, though there is some.
 
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#29
918v said:
Could have been the powder too. I have taken rounds apart where the base of the bullet was attacked by the powder and corroded.
Click to expand...
Yesterday, I took a look at the 4 remaining cartridges of Tubb's Final Finish bullets I loaded 6 1/2 years ago. Because of Tubb's coating on the bullet, not doubt it's not going to be the same as a bullet without the coating. But I was curious given the amount of time that's gone by.

There appears to be a little corrosion on the neck in the form of some whitish lines that corresponds to some whitish that can be seen just below the neck. It's something I've not seen before on cartridges I'd disassembled after several days from loading. I tried to get a good picture (see below) of that below the neck, but it just didn't show up as light as I would see it. It's not bright white, but it's there and only from the neck-shoulder junction down to the level of the powder.

Now that I think about it, I should've used my bore scope for a better picture. :rolleyes:

To removed the bullet, I put the cartridge in my seating die and pressed down to see if it would pop as an indication of it breaking free of being adhered. But, I didn't feel any of that and when I pulled the bullet with my Hornady collet puller, the bullet came out with no unusual effort. That was different from my cartridges that had sat of 6 months that had been seated in clean necks, where seating them lower did take a little extra effort, including an initial pop movement.

1726332484495.jpeg
1726332546039.jpeg


1726332592058.jpeg
 
#31
Cold welding is something that occurs with very clean materials. There must not be anything between the surfaces interfere with the movement of atoms between the two surfaces. Copper/brass by the way is one material that cold welds. Here is a good description of of the process.

www.twi-global.com

What is Cold Welding? (Advantages, Disadvantages and Applications)

Cold welding, or contact welding, is a solid-state welding process that requires little or no heat or fusion to join two or more metals together.
www.twi-global.com
 
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#35
I have lots of ammo that's been loaded for months or years. My graphite lube vs no lube expement I cooked for a few years was a bust. All bullets seated deeper just as easily as they seated originally, years later. Maybe I can find some old ammo that the bullets pop loose on. I would be interested to get a look at the surfaces with a microscope.
 
#36
I don’t think it’s corrosion. I think it’s a neck harness and neck tension thing. If it’s a soft neck and the neck tension is light then no pop. If the neck is hard and neck tension heavy then yes pop.
 
#37
The only two things I could think of, that I would believe would stick a bullet the way i experinced would be galling or corrosion. Galling wouldn't pop loose, it would continue to gall.


Do the bullets in the ammo you made pop if you seat them deeper?
 
#44
In recent years, photo- and electrocatalytic nitrate reductions have emerged as promising methods for sustainable ammonia production. Among the catalysts studied, copper-based systems have shown superior efficiency and selectivity in nitrate conversion, especially in the presence of sacrificial formic acid. However, the catalytic activity of copper is often hindered by its unstable oxidation state, primarily due to surface oxidation, and the underlying reaction mechanism remains poorly understood.
Click to expand...

Not sure this is what you’ve got going on though
 
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#46
The thing is I would think the wax layer from the Nufinish would insulate the brass from bonding with the bullet. So even if corrosion was present it would not be enough to cause the pop.

For the record the pop is slight, just barely noticeable but you can feel it and hear it.
 
#47
918v said:
And in your experiment where you did not feel a pop the brass was dry tumbled?
Click to expand...
In the experiment I didn't get any pop after a couple years. The 22-250 ammo I was just pulling down from a barrel I shot out much faster than expected. I pulled some 6arc down after having trouble with Rainer UM barrel and none of it needed broken loose after a couple months. All my stuff has always been dry tumbled the same, corn cob media with no additives.

The pop was not slight on my 22-250 ammo. All the 308 seated deeper like the day I seated the bullets. Rockchucker is a powerful press though.
 
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