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Campfire Tracker
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Campfire Tracker
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I've been reading about this in my spare time for a couple days! I believe it caused by case necks being undersized for the bullet. Along with case shrink over time! Since new brass seems to be resistant,annealed brass is more resistant, than used not annealed brass! Dirt and residue acts like a release agent. Bench rest shooters have many theory's. Since I have never experienced weld bonding, I'll accept the little knowledge I've gained, and call it good! It's just not that interesting any longer!
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'Four legs good, two legs baaaad." ---------------------------------------------- "Jimmy, some of it's magic, Some of it's tragic, But I had a good life all the way." (Jimmy Buffett)
SotG
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Joined: Oct 2004
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Campfire Ranger
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Campfire Ranger
Joined: Oct 2004
Posts: 16,916 |
Wouldn't bumping the seating depth a little bit take care of the cold welds? It sure helped with the asphalt sealed necks on a bunch of Lake City M118 & M852 ammo a friend had.
Somewhere I've read of a serious shooter who deliberately loaded his cartridges long if they weren't to be used right away. He'd seat to the correct depth before going to a match. . I seem to recall reading that "secondary seating" was an old trick used by shooters that loaded in large batches. Consequently some of that ammo may sit on the shelf for quite awhile. I've found some ammo that has been sitting for years on my shelves to be almost impossible to pull bullets using an RCBS collet die puller but when seated just a tad deeper they pulled normally.
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Joined: May 2005
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Campfire Tracker
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Campfire Tracker
Joined: May 2005
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I've been reading about this in my spare time for a couple days! I believe it caused by case necks being undersized for the bullet. Along with case shrink over time! Since new brass seems to be resistant,annealed brass is more resistant, than used not annealed brass! Dirt and residue acts like a release agent. Bench rest shooters have many theory's. Since I have never experienced weld bonding, I'll accept the little knowledge I've gained, and call it good! It's just not that interesting any longer! Bench rest shooters are commonly seen carrying a tray of primed cases at the range for this reason. Any incidence of weld bond will/can change accuracy as the release on the bullet cannot be uniform or reliable.
When truth is ignored, it does not change an untruth from remaining a lie.
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Good information on this issue from everyone and it will change how I do things in the future. I put this issue out there with our locals and the feedback was poor or disbelief. Recently my safe hunting loads became over pressure and pulling bullets was a chore, so I knew something was up. I kept a few as they were,seated a few a touch deeper and pulled and weighed the rest.I will chronograph these as well... Tony
Last edited by comerade; 03/31/17.
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Joined: Sep 2010
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Campfire Ranger
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Campfire Ranger
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Yes this is it and the last one I remember discussing. I searched 'cold weld' and didn't find what I was looking for. Thanx Jerry
jwall- *** 3100 guy***
A Flat Trajectory is Never a Handicap
Speed is Trajectory's Friend !!
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In Corrosion Control classes they told us similar metals in contact cold weld because, in the case of bullet and case, the copper atoms in the bullet don't know they aren't the same as the copper atoms in the case, so they adhere at an atomic level, sharing electrons. Or so the Chief teaching the class said. There is also galvanic corrosion, or welding together through electrical micro-voltage process which could be enhanced or encouraged by residual case lubes or cleaning detergents. But, I don't know for sure. Never studied it in cartridges. _________________________
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Campfire Kahuna
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Campfire Kahuna
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In Corrosion Control classes they told us similar metals in contact cold weld because, in the case of bullet and case, the copper atoms in the bullet don't know they aren't the same as the copper atoms in the case, so they adhere at an atomic level, sharing electrons. Or so the Chief teaching the class said. There is also galvanic corrosion, or welding together through electrical micro-voltage process which could be enhanced or encouraged by residual case lubes or cleaning detergents. But, I don't know for sure. Never studied it in cartridges. _________________________ Now we're cookin' ! ......the presence of Zinc (in solution) in the cartridge brass actually leads to / contributes to galvanic transfer, IIRC. GTC
Member, Clan of the Border Rats -- “Sometimes I wonder whether the world is being run by smart people who are putting us on or by imbeciles who really mean it.”- Mark Twain
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Joined: Sep 2010
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Campfire Ranger
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The mechanism by which it occurs is diffusion: where you have two similar metals in intimate contact, with nothing between them, atoms from one can diffuse into the other, and vice versa, across the interface. Essentially they wander about and forget where they are supposed to be, until enough of them have migrated that the boundary between the the bullet and case neck is blurred, and you have a joint.
This is very similar to what Pappy posted last year in the Sticky Bullet Syndrome thread. "Pappy348 Offline Campfire Tracker I did find this on Wiki under "cold welding": "The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and greases and more complicated thin surface layers of contaminants in between, the atoms “know” when they are not on the same part." — Richard Feynman, The Feynman Lectures, 12–2 Friction Thanks, John. Edited by Pappy348 (02/18/16)" _____ These things certainly sound reasonable. I just know from my limited experience with 'cold weld', I know what I used and what I didn't, and I know that powder 'Temp Sensitivity' was NOT the cause. Plus, after breaking the seal (weld)--the same--loads did not exhibit the xtra pressure signs. Jerry
jwall- *** 3100 guy***
A Flat Trajectory is Never a Handicap
Speed is Trajectory's Friend !!
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