The discussion about SS pin tumbling led to this thread. This will be a long post and I apologise in advance. I hope it's a worthwhile read.

I have never encountered this that I can confirm, so I can contribute little to this discussion, but I look forward to input from others. I will also explain what I do, which possibly disproves some of the causes suggested by others.

Quite a bit has been discussed about the phenomenon some refer to as "COLD WELDING", or "STICTION" or "GALVANIC FUSING" and a bunch of other things. Most of these descriptions actually have fairly specific scientific requirements from what I understand and are specific phenomena. Accordingly what people are experiencing and describing anecdotally is probably not correctly described as any of these, but these are all an attempt to explain what shooters are experiencing.

People describe loading ammo, to find a while later, be it over the course of days or years, that the ammo shoots poorly and displays high ES, or even highly increased velocity / pressures. Other anecdotal evidence relates to the difficulty some have experienced when pulling loaded ammo, with case necks tearing off with bullets still seated in some cases and huge effort required in other cases. Often a distinct "pop" is described as being heard as the "weld" breaks free when pulling ammo. There are so many factors involved in loaded ammo that it seems tough to single out what the causes of this are and how it can be avoided. As a result it seems most of what is suggested is merely anecdotal informed guessing.

This has led to some competitive shooters loading ammo long and reseating it shorter just prior to a shoot and others loading only days before important events. When reseating some again describe substantial effort and the "pop". I'm not a competitive rifle shooter, so I cannot question this practice, but I will say that not seating in a single operation from the case mouth seems to result in AOL all over the place, so I'm not sure this is a good solution to the "problem", if it exists.

Others suggest dipping case necks in graphite prior to seating so as to create an interference between the similar metals (see below). There seems to be some indication that doing so helps prevent this stickiness, but then this may have something to do with preventing corrosion with the coating, decreasing friction and a host of other things unrelated to the metals of bullet and case having direct contract. This became a popular recommendation when ultrasonic cleaners became popular. Some argued that the clean necks created too much resistance to pull, i.e. had the same effect as increased neck tension. I tried this and can't say that the rifle shot better. It's many years back now but I did see some change in velocity, but not sufficiently so to allow for a real conclusion. I also felt that I had no control over how much graphite the ceramic balls deposited on the neck (Redding ceramic balls and graphite "system"), so I stopped doing this. As I use this mechanism to "lube" necks for resizing, as I keep any form of liquid lube out of the neck, I brush necks prior to seating bullets. I generally just run a bronze brush on a drill press and it is a two second process and there is no graphite that remains visible to the naked eye, but possibly there is some trace left.

I generally use the same system when sizing with a Lee Collet die, but I have sized with no form of lube at all and noticed no difference, but I didn't run this as a test.

Attempts at explaining this has led to discussions around similar metals being pushed together under high pressure in the absence of air - hence the "cold weld" description. I'm pretty sure that the conditions for this to satisfy criteria for a cold weld are quite narrow and some people with technical knowledge have rubbished this saying that the requirements for this to occur cannot be met by seating a bullet; amongst others that the pressure is insufficient for this to occur.

This is where the argument has arisen that cleaning the case necks to bare metal is bad; the bare metal being required for this "fusion" to occur. I have often cleaned to bare metal with a bronze brush with no ill effects, but then maybe my neck tension is too little. I also frequently anneal my brass, which may prevent the occurrence. I have experienced differences in neck tension when sizing a batch of brass and seating bullets immediately and seating others a week later for example. The brass does seem to continue to "settle". However once the bullet is seated my experience is that the ammo is sort of "set" at that tension (i.e. the brass seems stable certainly from the point of view of affecting velocity).

The only posts I encountered by someone who seemed to have tried to actually isolate some of the causes were those from a gentlemen by the name of / posting under "Valentine" on the bench rest forums. As I recall Valentine believed the cause was (do I recall correctly!?) "stress corrosion"? He was of the opinion that not cleaning case necks increased the chances of encountering this, as did work hardened brass. In other words contrary to what many suggest, this gentlemen opined that bare metal was less likely to cause problems. He indicated that over time brass hardened and would change neck tension.

Some people seem to indicate that things changed when they changed the lubes which they used which makes me wonder if it could relate to the removal of lube after sizing, but competitive shooters are quite and anal bunch and I cannot imagine that this is a cause in all cases.

There is also a host of evidence to indicate that ammo years old is shot with no ill effects and sometimes shooting to the same POI as more recently loaded ammo.

My view is that nobody seems to refer to this phenomenon when loading virgin brass (bare metal), or when shooting factory ammo (bare necks I think), often loaded months or even years previously. Is it the seal around the case neck preventing the ingress and egress of moisture that helps? Or the factory crimp where necks are not sealed? I've not been able to establish that ammo companies specifically coat case necks inside, or bullets, to counteract this occurrence which makes me wonder why reloaders experience it seemingly with brass fired multiple times. Could it be that my frequent annealing is preventing it from causing me problems? Possibly it is climate in which I live that makes a difference! Or the short neck of the .300 Win Mag with which I have done by far the most shooting to date Maybe my ammo is just never old enough, but then I've fired some older ammo and factory ammo from the 1980's with no ill effect and some of my big game hunting ammo is now about eight years old.

Accordingly I am quite certain that under certain sets of conditions this phenomenon does occur. Maybe we need to try to recreated this and attempt to isolate the possiblle causes one at a time.

I welcome any input on your experiences.

Question:
HAVE YOU EXPERIENCED THE PHENOMENON DISCUSSED BELOW SOMETIMES CALLED STICTION OR COLD WELDING?

Choices:
YES
NO
EXPERIENCED SOMETHING OF THIS NATURE BUT NOT SURE

 

Can you do an concise executive summary of your post?

The only cold welding I have experienced is a reaction that takes place between steel pins used in aluminum actions.