Bullet Weld related to cleaning method?

[Doom]

@JFrank posted on an older thread concerning neck tension and time between prepping and loading that reminded me of another question that I have been curious about.

The issue that is commonly referred to as bullet welding refers to a phenomenon that is unlikely to occur in a normal environment. because it requires a super clean environment for the two surfaces to allow migration of the material to occur. However I acknowledge that something is going on and I believe that the case cleaning method may be the factor that is leading to this condition.

Dry cleaning method such as tumbling in walnut or corncob media doesn't normally remove the normal oxidation layer in the neck or introduce contaminants that would affect the cleanliness of the case. Wet Tumbling or ultrasonic cleaningnwith various additives and tap water introduce the possibility of removing the oxide layer and introducing contaminants to the case.

If you have experienced this phenomenon can you share your cleaning method and any bullet seating "additives" used?

 

[JFrank]

While I’ve experienced bullet welding in the past, my current method is to not clean brass beyond wiping the case with a paper towel and burnishing the neck ID with a nylon bore brush prior to seating. Since I’ve adopted this method I seem to be free of the dreaded bullet weld.
Jim

 

[SeabeeKen]

I have experienced bullet weld both after dry and wet cleaning. Recently, I've experienced it with some 308 rounds that had only been loaded for 3 weeks. This was new PPU brass and they were test loads. At the last minute I decided to use a different bullet and so started pulling bullets. Of the 30 I had loaded, I had 5 that could not be pulled with my collet puller without first seating deeper to break the bond. These cases were virgin unfired. in the 50+ years since I started handloading, I have loaded fired cases uncleaned but back then I didnt pull bullets so I cant atest to weld at that time. IME, carbon in the necks seems to mitigate weld IF the carbon isn't removed during bullet seating. I am currently using Neolube 2 inside my necks and so far havent noticed weld on the few I have had to pull. Bullet weld is real and about 10 years ago I wanted to pull some hunting bullets that had been loaded 2 years.None would pull. I decided to seat them deeper to break the bond and the resulting pop was so load my wife came down thinking a round went off. The pop was about like a primer going off. My conclusion was if the 2 metals are in contact, weld can happen.
I have used graphite and HBN in necks bout have yet to have to pull any of those bullets

 

[K22]

I do not tumble anymore but clean the exterior necks with 0000 steel wool followed by spraying the exterior with mineral spirits then wiping clean with a Scott Shop rag. This simple, quick, and effective method works perfectly for me.

I nylon brush the interior of the necks before sizing.

While I do not shoot to the level of precision that a lot of members do, I often pre-load ammo in the winter months for upcoming spring and summer shooting seasons which are more active than my winter shooting program. I have been unable to detect any effect on target, of reload pre-load months ahead shooting at the varmint level accuracy standards.

However, I cannot deny the claims and experiences of other precision shooters of this forum. I would say that if is one is concerned with "bullet weld" but also has a need to pre-load ammo, seat the bullets out and re-set before using them. Just make sure you place a clear and unmistakable marker on the cartridge box to remind you to re-set the bullets before shooting

 

[searcher]

I've run into various levels of bullet weld over the past 5 decades of reloading, having pulled a lot of bullets and running so much over the chronograph. Because of this, I've changed how I clean my brass and how I load. First, if I'm running bare bullets (which I do in most of my target rifles which do not have a hard jamb load), I shun any type of tumbling that removes all the carbon inside the neck which, in my case, "bad" removal mostly came from ultrasonic wet cleaning. I imagine the stainless pins some folks use would do the same or worse. I tumble my brass for about 20 minutes in crushed walnut shells after firing to keep my dies clean, and again for about 10 minutes after sizing to remove lube. Pretty cases look nice, but I don't want to remove that carbon in the neck - I just run a brush once in and out. If I'm using my hand dies for target loads, I wipe off the case after firing, clean the outer neck (if needed) with gray abrasive "sponge" and once in and out with the neck brush.

For ammo that I preload for my target rifles, if I'm shooting it the next day or two, I set to my final depth. If I'm loading up a bunch of practice ammo that may be used over a period of months (or maybe even years in a rifle I don't shoot much), I'll seat them about .010" long. I used to seat them only about .002" long but found that if there is moderate cold weld, the shoulder will actually push back that much before the bullet breaks loose. And that was a good lesson learned, as pushing back the shoulders a few .000" does no good to any load for consistent shooting. So - when pre-loading, I ALWAYS tried to have any match ammo loaded as close to a match as possible (no more than a few days if possible), and seated to final depth or do a re-seat on ammo with light neck tension just before match. I read of guys re-seating their crimped A/R ammo which has sat around for a long time. If they measured their brass shoulder-to-base ("headspace") measurements before and after re-seating, they would see why their rifles still didn't shoot well with the re-seated ammo. Some end up with failure to fire on some rounds and blame it on "old" ammo, yet it was due to the excessive headspace they created when re-seating the bullet.

On my varmint ammo (and a few match rifle barrels that I heavily jamb the bullet), I prefer moly on the bullets. I've pulled a lot of moly bullets over the years and they come right out compared to bare bullets. Stored ammo has also shown significantly tighter SD's after storage with moly as opposed to bare.

So, in short, I'd not overclean the necks and try to load match ammo a few days before the match. If you want to load match ammo that might not be used for months or more- I think using moly is the only way to best avoid the other problems that come with bullet friction change, reseating issues, etc.. I've used the neck lubes, moly paste and a lot of other methods to treat the neck to prevent these problems and most do work to some degree, especially over the short term. I'd rather not use them over the long term - but rather use the bullets that are treated.

 

[Doom]

Thanks for your input. I had hoped for more comments. My experience is anecdotal as I've not experienced any detectable issues with the rounds I have deconstructed. My oldest rounds are normally about 2 years old. I used corn cob media for several years then went to ultrasonic but the issue of cleaning solutions and the possibility of adding potential corrosive elements drove me away from this method. I now use Lizard litter walnut media. It doesn't plug flash holes.

I am a mechanical engineer not a metallurgist so I'm not sure about the molecular aspects of cold welding but the two factors that I know are required are cleanliness and ductility which implies that annealing may play a part in the issue.

It seems to me after looking at this issue the simplest solution is to allow dry cleaned resized brass to sit for a while (days or longer) to allow any exposed metal to form an oxide layer that should prevent any "welding" to occur. In lieu of that then the addition of graphite or other compounds would likely prevent the problem from occurring.

One thing that I have never understood is the wet cleaning with stainless steel pins. The pins will not only remove any surface coating and expose bare brass.

 

[Krogen]

I am a mechanical engineer not a metallurgist so I'm not sure about the molecular aspects of cold welding but the two factors that I know are required are cleanliness and ductility which implies that annealing may play a part in the issue.

I'm an electrical engineer. (Don't hold that against me!) We use cold-welding to join high current electrical terminations. In addition to cleanliness and ductility, an effective cold weld requires high pressure. Basically it's mashing two clean and ductile materials together so that there's a molecular bond. Not all materials are suitable. Oxide layers can get in the way of a good molecular exchange.

Bullet jacket and case alloys may vary among various suppliers. Neck tension varies depending on the loading process. I suspect these variables, along with cleanliness and ductility, work in concert to make a bullet "stick" or not. Unfortunately, I don't have answers; only questions.