Cold welding of bullets in case necks and moly coated bullets

[JRS]

Metalergists will always tell you that like metals put together will have a chemical reaction to one another. Whether it is caused by moisture or not, it makes no difference.

Did you mean to say "unlike" metals (dissimilar) as in galvanic reaction of which moisture could be the electrolyte required to initiate the reaction? I'm wondering if the salts from sweat from your fingers could be the catalyst. My eldest is a "ruster", every bare piece of steel he handles leaves rust fingerprints or worse. On occasion I have pulled bullets he reloaded and they could not be pulled with an impact puller. Note that they were definitely not crimped. These pulled bullets always have a narrow black ring around the bullet and underneath that black substance there is a definite groove that takes a few passes with steel wool to remove. I would think that besides body salts, any cleaner or oil that has a high Ph might also serve as a catalyst. Remember also salt tends to attracts moisture (humidity).

One of the reasons I wear nitrile gloves

 

[Lenard]

LH, I apologize, as you are correct. I usually proof what I write as things do not always translate to paper correctly at my age. Part of this equation provide more questions. I apparently do not have salt in my sweat that effects a finish on firearms or bullets that are around. Makes me wonder if as an example, are varmint bullets made with the same alloyed copper as say a heavy big game bullet. Or is it just the thickness of the jacket that makes it tougher on big game bullets.

Thanks for pointing out my error.

 

[Brians356]

When did the supposed vacuum inside the case form?

When seating a bullet, if anything internal pressure (opposite of vacuum) is created since the bullet compresses the internal air (assuming no leakage past the bullet or primer.)

Over time, again without leakage, that pressurized state would remain static indefinitely. Where's the vacuum?

I take the sound of crickets as acquiescence. There is no vacuum. At least not a vacuum that could render the bullet immovable.

 

[suberjc]

Do you have any personal experience with the phenomenon that is referred to as cold welding of bullets in case necks? I am not saying that the bonding is actual cold welding, but there is some sort of strong bond that can form.

Well now see, I see the same thing (an increase in break point from the first max at the second seating) if I turn around and do it 30 seconds after the first seating.

I dunno. I'm just saying. I've seen high 590s (F) with bullets seated a month early and with ones seated the night before. Never tried a combination. I'll let you guys tell me how that turns out.

 

[BoydAllen]

What you are seeing, and what this thread is about are not the same thing at all. When what is referred to as cold welding takes place, it takes a lot of pressure on a reloading press handle to move the bullet deeper and when it does move, there is an audible pop, as if something that was fully bonded had broken loose, and and after that the force required to move the bullet is like normal seating force. It is common in discussions about this subject that fellows will post who have not experienced it. It happens all the time.

 

[Turbo900rr]

I think to properly prove or disprove the theory a person needs to load 10 rounds, wearing gloves in low humidity(winter) and from the same lot numbers of powder,brass, bullets and primers load ten more rounds six months later and go out and shoot all 20 rounds at a decent distance, say 300 yards and let the groups speak for themselves. (Sorry if idea is reposted, didn't read all pages)

 

[LHSmith]

I think to properly prove or disprove the theory a person needs to load 10 rounds, wearing gloves in low humidity(winter) and from the same lot numbers of powder,brass, bullets and primers load ten more rounds six months later and go out and shoot all 20 rounds at a decent distance, say 300 yards and let the groups speak for themselves. (Sorry if idea is reposted, didn't read all pages)

Better a 100 or 200 yard ballistics tunnel from a machine rest, with the bore fouled the same before each group and the barrel at the same temp before each group and shoot 5 five shot groups alternating between new and previous loads. Now to figure out in what environment to store the pre-loaded rounds for those 6 months. Such testing could be never ending as some variables are out of our control - jacket and brass metallurgy, powder chemistry to name a few.

 

[Brians356]

I think to properly prove or disprove the theory a person needs to load 10 rounds, wearing gloves in low humidity(winter) and from the same lot numbers of powder,brass, bullets and primers load ten more rounds six months later and go out and shoot all 20 rounds at a decent distance, say 300 yards and let the groups speak for themselves. (Sorry if idea is reposted, didn't read all pages)

I don't know if you are referring to alleged "cold welding" or the gradual spring-back of the neck brass (i.e. simple increased neck tension), but it would likely take many more than 10 rounds each to prove or disprove the theory, and it's all subject to the usual random vagaries induced by homo sapiens behind the butt anyway.

Something as simple as, say, ~100 lbs force required to seat a bullet deeper (vs ~15 lbs when first seated) and an audible "pop!" when it moves seems a valid enough proof that some bonding has set in, anyway.

PS

I have some 270 Win deer loads, sitting idle since the 1990s. The 140-gr BTs were seated near or touching the lands, RE-22 powder, and fairly stiff loads, at or slightly above typical book maxima (or shall I say book max velocities, but from a 22-in barrel vs books' 24-in.)

Recently I took them out to chronograph them, and frankly, to just get rid of them, as there were only about 15 remaining, and they have gotten too old. I got something of a shock from the recoil, and I could hardly lift the R-77's bolt handle. Primers as flat as I've ever seen, cratered, and extractor marks very prominent. I shot two of them and stopped. They clocked about 150 fps higher than I expected as I recall.

After following this thread, I'm now going to seat the remaining bullets about .010" deeper, paying attention to force required, and then shoot some again. I want to know if the powder has undergone a transformation, or if this is an example of bullet/neck bonding. (These have been stored in a cool dry closet, in dry Nevada, and no visible corrosion evident, anyway.)