What is the Cold Welding I hear about ?

Munkey1973

Munkey1973

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Last season at a local F Class match, I witnessed a couple guys (one a F Open, the other was an F T/R such as myself) …. local champion-type shooters .. the cream-of-the-crop local shooters, where seating their bullets on the back of their half-tonnes with abor presses and Wilson Seating type dies.... moments before their time to shoot.

When I asked, according to the F Open guy, he does everything else to his loads during the dead of winter (i.e. primes, powder charge, and seats a bullet just a little ways in to stop powder from exposure) and then he seats the bullets to the right depth just a few moments before his turn to shoot on his rely.

If I understand correctly, the justification to this practise is something like this, "if the bulllets sit for too long, then the neck tension between loaded rounds will lose their consistency"... put differently, some may hang up (and effectively "stick a bit to the brass or weld to the brass") and others may not.... of course, this will lead to inconsistent bullet release and undesired increased elevation dispersion.

Is this line of reasoning factual, has anyone empirically tested this theory, or is it merely subjective ?
 
It is in fact, a real phenomenon, particularly if the brass is cleaned with SS pins,
or is brand new and shiny inside the neck.
I have had loaded rounds pull part of the neck right off the case when fired.

This was brand new Starline brass in 38-55, bullet was the Barnes original 255
grain JSPFN. I had loaded it several months earlier. I tried pulling the rest after
a couple lost the forward part of the case on firing. about half would not budge.

I peeled back the brass case from those bullets, and it was like a solder bond.

Never had it happen with brass that was previously fired and not cleaned with pins.
A little bit of carbon left in the necks seems to prevent the welding. Dave.
 
Last edited:
Good Afternoon

Cold welding, or galvanic corrosion is a process where dissimilar metals react and switch electrons and "weld" to one another.

It seems to be more prevalent the cleaner your brass... ultrasonic or stainless steel pin.
Best practice for avoiding the problem is to seat a few thousandths long of your seating depth and finish seating as close to when you want to shoot the rounds as possible.

Conversely less cleaning leaving carbon in the neck or adding graphite or other dry lubricant, reduces or eliminates this issue.

As an F/TR shooter I seat long because I travel to matches. Leaving the rounds long allows me to seat the bullets to my desired length for consistency.

Trevor
 
Smcx said:
If this is such a problem, why don't 50 year old military-surplus rounds have this issue?
Click to expand...

Military cartridges have their bullets crimped. A crimp will cause more resistance to release the bullet than any "cold weld". This issue is only a bit of a problem for precision shooters and accurate handloads.
 
This is all very helpful to know.

I do wet clean my brass with stainless steel pins. I also use a homemade induction annealer (it after every firing) and run about 0.002-0.003 neck tension. I usually make my loads no more than a week before a match.

Eagleye, I don't use Starline brass, but after hearing your experience, I will definitely look into using a dry lube if I choose to continue SS pin cleaning.
 
I had some ammunition I made up then went to pull as I didn't like the load. The force needed to pull some of the bullets was incredible. I actually thought I was going to tear some of the casings in half before the bullet let go. Could cold welding be that extreme?
 
Back when I was learning the basic atomic properties of metals, I remember a professor telling the class that if you took two blocks of compatible metal and simply pressed them together by hand, they would instantly become a single, solid, seamless block, IF you could get the mating surfaces completely clean. It has to do with the mechanism of metallic bonding, wherein each atom shares electrons in its outer orbital shell with neighbouring atoms.

In reality, corrosion products, adsorbed oxygen and other foreign substances prevent the individual atoms from getting close enough to share electrons in normal circumstances, but it does sometimes happen when two metals slide past each other with high normal loads, which disrupts the impurities and leads to welding at the peaks of asperities. The asperities then break off under further sliding motion and leave a broken and gouged surface. This mechanism is known as galling.

Trevor60 said:
Cold welding, or galvanic corrosion is a process where dissimilar metals react and...
Click to expand...

Cold welding and galvanic corrosion are completely unrelated. It is true that galvanic corrosion requires dissimilar metals (as measured by reduction potentials in an electrolytic half cell). Cold welding on the other hand, is more severe if the materials share some common properties, such as crystal structure.
 
Ammunition inspection and testing may include measuring bullet pull - how strong a pull is needed to remove a bullet from a round. In the early '20s, there were experiments in the US with tin plated bullets, the intent being to stop nickel fouling rifle bores. The tin coating resulted in bullets getting bonded to the cases. If I remember the numbers correctly, bullet pull could be hundreds of pounds. The experiment was rapidly terminated.

When a round fires, the case expands. The bullet is released - it doesn't just get pushed out of the neck.
 
This !
Its called a diffusion weld. . All u need is two extremely clean metals ( no oxidation) in close contact .
Generally u need to add pressure and some heat
Ive done alot of diffusion welds with ferrous and non ferrous metals.
If the oxidation layer is thin.. a weld can take place when extreme pressure is applied
It wont be the strongest weld as micrograph will show an oxidation layer within the weld boundary.
If u have a large hydraulic press or rolling mill u can do this




BattleRife said:
Back when I was learning the basic atomic properties of metals, I remember a professor telling the class that if you took two blocks of compatible metal and simply pressed them together by hand, they would instantly become a single, solid, seamless block, IF you could get the mating surfaces completely clean. It has to do with the mechanism of metallic bonding, wherein each atom shares electrons in its outer orbital shell with neighbouring atoms.

In reality, corrosion products, adsorbed oxygen and other foreign substances prevent the individual atoms from getting close enough to share electrons in normal circumstances, but it does sometimes happen when two metals slide past each other with high normal loads, which disrupts the impurities and leads to welding at the peaks of asperities. The asperities then break off under further sliding motion and leave a broken and gouged surface. This mechanism is known as galling.



Cold welding and galvanic corrosion are completely unrelated. It is true that galvanic corrosion requires dissimilar metals (as measured by reduction potentials in an electrolytic half cell). Cold welding on the other hand, is more severe if the materials share some common properties, such as crystal structure.
Click to expand...
 
Hey, thanks to all who are in-the-know and have chimed in on my opening post!

Seems there were no posts that offered scientific theory/evidence that the claim phenomena of Cold Welding (of a bullet to its case) is a hoax or urban legend.

So I am now going to accept this is fact.

That being said, I still want to continue to Wet Stainless Steel tumble my brass.
I am not keen on the idea of running carbon covered brass through my nice Redding dies.

The use of a dry lube (or graphite) has already been mentioned as a mitigator of this problem.....

What if a guy left a thin (i.e. residual) coat of Redding resizing wax on the inside of the neck (I apply some when trimming and/or neck-turning) ?

Could this stop the cold bonding of the two surfaces ?
 
Eagleye said:
It is in fact, a real phenomenon, particularly if the brass is cleaned with SS pins,
or is brand new and shiney inside the neck.
I have had loaded rounds pull part of the neck right off the case when fired.

This was brand new Starline brass in 38-55, bullet was the Barnes original 255
grain JSPFN. I had loaded it several months earlier. I tried pulling the rest after
a couple lost the forward part of the case on firing. about half would not budge.

I peeled back the brass case from those bullets, and it was like a solder bond.

Never had it happen with brass that was previously fired and not cleaned with pins.
A little bit of carbon left in the necks seems to prevent the welding. Dave.
Click to expand...


I consider myself lucky as I have yet to have any problems and I have been using SS pins for quite a few years now.

I just recently pulled some bullets from some 6.5 TCU cartridges and they pulled fine without any troubles, I was wondering if there might be a problem with them after sitting for 2 years.

One thing I have started recently is to use wash and wax car wash as a rinse and on bottle neck cartridges I use the Imperial dry lube so I am hoping that I will not have any problems.
 
Happened to me on a 6.5/284 lapua brass 130 Berger loads from a few years back. Shot terrible. Went to re-seat deeper the same batch and heard the pop of the bullet as it cracked the “cold weld”
I don’t use pins and this was 1x fired brass. Hmmm
 
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