is copper jacket spinning around lead core during flight

Time has everything to do with heating something.
As I said early in the piece, lead does not melt inside the jacket, there simply isn't enough time for the heat to do so.
Look at it like passing your hand through a blow torch flame, do it quickly and you do not get burnt, hold it there….and well.
Lead cores are lubed, cores can slip, this is known. Jackets are thicker than .004", most grooves are this deep, if you section a bullet that has been fired, the rifling is not evident on the inside of the jacket, it doesn't displace enough material.
If you have ever used a roller to put cannelures on bullets, you will know just how much displacement is required to make the groove deep enough, it is on the order of .050-.060" deep and locks the core in place 90% of the time.
Anyway, bullets get hot, but not enough to melt the core while travelling down the barrel or through the air. They get far hotter after expanding in a medium, no matter what that medium is.

Cheers.
 
I just registered to ask if anyone's interested in reviving the discussion on spinning bullets and molten lead. If so I have some interesting info and photos to share that will show the end result of molten lead cores but will also spark more questions and discussion.
 
So way back in 1979/1980 I was hand loading my new Weatherby Mark V rifle in 270 Weatherby Mag. With no guidance, I started to load the 130 Grn. Sierra GK faster and faster, My ridiculous thought back then was that faster must be better for killing Mule deer. So, I pushed the limits and tried for 3500 fps. I do not think I ever achieved that velocity , but on the way to that number, I noticed lots of Grey Lead Splatter on the paper targets at 100 yards. I backed off the powder charge at once, and the splatter went away. I always wondered if the lead melted inside the copper jacket, and was still liquid at 100 yards. I never thought about the jacket spinning around a molten lead core. I never did that again, I learned "Just because you can, that does mean you should."
 
Bob Wright said:
So basically I think it's all solid just due to barrel time and time of flight. This is not a returning space capsule at 25,000 mph for 5 minutes . Exposure to all the heating is way too short to liquefy the core or jacket.
Click to expand...
This comment caused me to think about the question of "how much heat is generated by just the bullet moving through the air?" As you've said, the time of flight is so short that I'm also doubting that the bullet sees a huge delta-T, but it does make me wonder. I haven't read Mr. Litz's book, maybe I should. Is there even such a thing as a high speed IR camera? If there is, I'm betting that it's made by FLIR and mere mortals can't afford one.
Clearly the faster the bullet goes, the more heat generated, but how much heat is that? If the average speed of the bullet is 3500 fps, then a mile is only about 1.5 seconds flight time, so most flight times are going radically shorter - meaning not much time to generate much heat. Can it be quantified as so many BTU's per 100 FPS?I'm guessing that it's more complex than that. With enough study could a Rule of Thumb be developed to address this? Does the elevated temperature of the projectile alter the ballistics? Would any of it even matter?
 
Lenny Foffa said:
I do not think I ever achieved that velocity , but on the way to that number, I noticed lots of Grey Lead Splatter on the paper targets at 100 yards. I backed off the powder charge at once, and the splatter went away. I always wondered if the lead melted inside the copper jacket, and was still liquid at 100 yards. I never thought about the jacket spinning around a molten lead core. I never did that again,
Click to expand...
Interesting that you should happen to "capture" that. Out of curiosity, was it like a smudge like coating or droplets? Seems like if it were molten lead and particles that had enough mass, there would be burn marks on paper.
 
ntsqd said:
This comment caused me to think about the question of "how much heat is generated by just the bullet moving through the air?" As you've said, the time of flight is so short that I'm also doubting that the bullet sees a huge delta-T, but it does make me wonder. I haven't read Mr. Litz's book, maybe I should. Is there even such a thing as a high speed IR camera? If there is, I'm betting that it's made by FLIR and mere mortals can't afford one.
Clearly the faster the bullet goes, the more heat generated, but how much heat is that? If the average speed of the bullet is 3500 fps, then a mile is only about 1.5 seconds flight time, so most flight times are going radically shorter - meaning not much time to generate much heat. Can it be quantified as so many BTU's per 100 FPS?I'm guessing that it's more complex than that. With enough study could a Rule of Thumb be developed to address this? Does the elevated temperature of the projectile alter the ballistics? Would any of it even matter?
Click to expand...
Some of the night-time wild hog hunts I've watched where they use IR night vision you can see the bullet hit and go through the hog then fly off into the dark.
 
ntsqd said:
This comment caused me to think about the question of "how much heat is generated by just the bullet moving through the air?" As you've said, the time of flight is so short that I'm also doubting that the bullet sees a huge delta-T, but it does make me wonder. I haven't read Mr. Litz's book, maybe I should. Is there even such a thing as a high speed IR camera? If there is, I'm betting that it's made by FLIR and mere mortals can't afford one.
Clearly the faster the bullet goes, the more heat generated, but how much heat is that? If the average speed of the bullet is 3500 fps, then a mile is only about 1.5 seconds flight time, so most flight times are going radically shorter - meaning not much time to generate much heat. Can it be quantified as so many BTU's per 100 FPS?I'm guessing that it's more complex than that. With enough study could a Rule of Thumb be developed to address this? Does the elevated temperature of the projectile alter the ballistics? Would any of it even matter?
Click to expand...

Here is what I was told by a whitetail guide when I asked him if he had a preference for a good whitetail cartridge.

" I always recommend a 30 caliber cartridge. I do this because the remaining bullet is only about 7mm by the time it hits the deer". I thought he was just joking so I asked him how he figured that. He responded," there is so much friction with the air that the bullet burns down in diameter. Some bullets might actually get smaller than 7mm if the flight time is long enough".

That is the sum and substance of that conversation. I did ask him if he ever recovered a bullet from the dirt berm behind the lodge. He didn't answer. :rolleyes:
 
Varmint Hunter said:
Here is what I was told by a whitetail guide when I asked him if he had a preference for a good whitetail cartridge.

" I always recommend a 30 caliber cartridge. I do this because the remaining bullet is only about 7mm by the time it hits the deer". I thought he was just joking so I asked him how he figured that. He responded," there is so much friction with the air that the bullet burns down in diameter. Some bullets might actually get smaller than 7mm if the flight time is long enough".

That is the sum and substance of that conversation. I did ask him if he ever recovered a bullet from the dirt berm behind the lodge. He didn't answer. :rolleyes:
Click to expand...
Omg. These are the kind of conversations I love to get into and agree with them and feed them more rope just to see how far the craziness can get. Entertainment if you don't blow it and bust up laughing.
 
ntsqd said:
This comment caused me to think about the question of "how much heat is generated by just the bullet moving through the air?" As you've said, the time of flight is so short that I'm also doubting that the bullet sees a huge delta-T, but it does make me wonder. I haven't read Mr. Litz's book, maybe I should. Is there even such a thing as a high speed IR camera? If there is, I'm betting that it's made by FLIR and mere mortals can't afford one.
Clearly the faster the bullet goes, the more heat generated, but how much heat is that? If the average speed of the bullet is 3500 fps, then a mile is only about 1.5 seconds flight time, so most flight times are going radically shorter - meaning not much time to generate much heat. Can it be quantified as so many BTU's per 100 FPS?I'm guessing that it's more complex than that. With enough study could a Rule of Thumb be developed to address this? Does the elevated temperature of the projectile alter the ballistics? Would any of it even matter?
Click to expand...
Someone like Litz could do the complicated thermodynamics on this subject but I don't know if it matters. I don't believe bullet heating changes any BC related data. The only company that even brought up melting plastic tipped bullets was Hornady. No other company that I'm aware of.
Hornady's "Heatshield" white paper is attached. Hornady clearly states aerodynamic degradation did not apply to Hollow Point or Spitzer Point (lead) tips. That would lead me to believe that the lead mass is not melting due to heat transfer.
 

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I was shooting 130gr Nosler Partitions ( Exposed lead tip ) through a .270wby magnum at some outrageous velocities and never had any indications of tip deformation or melting. Also shot 130gr Balistic tips through it and again no evidence of anything going awry on the target.
 

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