is copper jacket spinning around lead core during flight

[Professor Doolittle]

Habu (SR-71) flew at Mach 3+ and the leading edge temperature never exceeded 600° F (316° C) on long missions. It took minutes at speed for the windshield exterior temperature to get above 450° F (232° C) not enough to even melt Pb (Lead) but they used a Titanium Alloy skin and a man-made Quartz outer layer for the windshield.


That wasn't at sea level.

 

[Professor Doolittle]

Some thoughts:

• It's less heat from the burning powder, because the bullet is being pushed by a powder column as it burns up from the bottom, and more from the friction pushing it down a barrel. Common sense dictates that you would expect this phenomena to occur more frequently in longer barrels.
• For kicks and grins, fire a shot into a shallow portion of a lake so you can fetch the otherwise untouched bullet, and then section it.
• I would suspect that your stability would go out the window because your spin rate would drop precipitously due to the internal friction created by the lead phase change, and the copper would slow to whatever the lead core was spinning at.
• Sounds like a good reason to start using monos exclusively.

What's a mono? A bullet that's not a composite?

 

[P7M13]

What's a mono? A bullet that's not a composite?

Mono-metal, aka copper or manganese.
I've only seen Mn bullets from Midway.
For coppers, manufacturers include Hammer Bullets, Lehigh Defense, Cutting Edge, Barnes TSX, American Cu Bullets, Peregrene, Hornady GMX, and Nosler E-tips, to name a few.

 

[Professor Doolittle]

So if the core melted, why do you get jacket separation that many times the jacket is found in an animal, but the core passes through and makes an exit wound? How would molten lead continue to travel through without dispersing to nothing? Maybe there is a reason that they make the base of the jacket thicker then the sides? Way back when, Sierra and some other bullet makers used to make their match bullets with an open base where you could actually see the lead core. If the core melted, wouldn't the lead run out while the bullet was in flight? Actually, aren't FMJ bullets still make like that? Think about it.

That's interesting, I didn't know hunters find copper jacketing with missing lead. If the tail was exposed lead and the lead melted I don't see why you would expect it to drain out in flight. Its being pushed from behind as it leaves the barrel so all lead and copper atoms have the same velocity, doesn't matter if its liquid, the bullet is falling the instant it leaves the barrel and all atoms in the bullet are falling at the same speed. If you could drop a glass of water upside down the water wouldn't come out because the glass is falling just as fast as the water is. The moment it leaves your barrel the bullet is falling.

 

[shootallday]

I've pushed 50 grain sp bullets over 4000 fps from a 22-250ai with a 1-12 twist and the same from a 1-9 22-250 but closer to 3900.

 

[esshup]

I've "poofed" 175g 7mm SMK's. My only thought was the throat got a wee bit rough and weakened the jacket enough so that they exploded around the 50 yd mark. 1:9 twist 3490 fps. The first 200 shots were fine, then things started to go haywire. Nothing made it to the 100 yd target and when I lifted my head from the scope to try and see the bullet impact that's when I saw the grey cloud.

I also shot that gun at night, no external light with a GoPro and another video camera. Wanted to see the size of the blast flash from the muzzle brake. In ONE frame in ONE of the videos there is an orange streak in front of the muzzle blast that looks exactly like a bullet. I can't explain why it showed up on that one frame in the video, nor why it was that color. There was no external light source except a full moon which was behind me as I shot.

 

[shootski]

Habu (SR-71) flew at Mach 3+ and the leading edge temperature never exceeded 600° F (316° C) on long missions. It took minutes at speed for the windshield exterior temperature to get above 450° F (232° C) not enough to even melt Pb (Lead) but they used a Titanium Alloy skin and a man-made Quartz outer layer for the windshield.



That wasn't at sea level.

That's why I used Mach Number and not airspeed.

 

[Professor Doolittle]

That's why I used Mach Number and not airspeed.

Well I learned something because I didn't know mach values were normalized against pressure altitude. How I never knew that I don't know but I never studied aerodynamics. My background is semiconductor engineering, I made rf transceiver chips for Apple's early iPhones and the first iPad before I retired.

 

[Professor Doolittle]

I've "poofed" 175g 7mm SMK's. My only thought was the throat got a wee bit rough and weakened the jacket enough so that they exploded around the 50 yd mark. 1:9 twist 3490 fps. The first 200 shots were fine, then things started to go haywire. Nothing made it to the 100 yd target and when I lifted my head from the scope to try and see the bullet impact that's when I saw the grey cloud.

I also shot that gun at night, no external light with a GoPro and another video camera. Wanted to see the size of the blast flash from the muzzle brake. In ONE frame in ONE of the videos there is an orange streak in front of the muzzle blast that looks exactly like a bullet. I can't explain why it showed up on that one frame in the video, nor why it was that color. There was no external light source except a full moon which was behind me as I shot.

I'm baffled as to why the first 200 shots would be fine. Why would the throat become a problem after 200 rounds? Why couldn't it be that the barrel broke in after 200 rounds causing a further increase in speed that exceeded the capacity of the bullet in some way, maybe by spinning it too fast. I mean that's 0 to 279,200 rpm in about 2 milliseconds!

 

[DarryH]

there have been multiple bullets that have bonded cores. Some on a molecular level.

 

[Rflshootr]

That's interesting, I didn't know hunters find copper jacketing with missing lead. If the tail was exposed lead and the lead melted I don't see why you would expect it to drain out in flight. Its being pushed from behind as it leaves the barrel so all lead and copper atoms have the same velocity, doesn't matter if its liquid, the bullet is falling the instant it leaves the barrel and all atoms in the bullet are falling at the same speed. If you could drop a glass of water upside down the water wouldn't come out because the glass is falling just as fast as the water is. The moment it leaves your barrel the bullet is falling.

Ok if the lead melted while it was being pushed down the barrel, and the nose of the FMJ wouldn't allow the liquid past it, wouldn't the liquid squirt out the rear from the pressure? If you took that glass of water and blew a air hose at the opening, no matter what position it was in, would the water stay in the glass?
And yes I have found plenty of jackets with no core.....it's called core separation. It happens more with non bonded boat tailed bullets without a cannelure as opposed to flat base bullets. That's the reason Hornady did the interlock and others do the bonded bullets.

 

[Gone Ballistic]

Slow down gentleman. The bullet is getting it's speed from the gasses released by the powder burning. Because it is ahead of the high level of temperature of the burning powder for milliseconds it gains more heat from speed through the atmosphere than it does in the barrel. Non-bonded bullets jackets can become separated from the lead at high twist rates and excessive speed.

 

[Rflshootr]

Slow down gentleman. The bullet is getting it's speed from the gasses released by the powder burning. Because it is ahead of the high level of temperature of the burning powder for milliseconds it gains more heat from speed through the atmosphere than it does in the barrel. Non-bonded bullets jackets can become separated from the lead at high twist rates and excessive speed.

Exactly the point I was trying to make.....now, does the heat/ friction from speed cause the jacket to get hot enough to make the lead liquefy and become loose? I say no.....it's the rotational forces from the high twist rates.......which really makes the jacket come apart at the weak spots from engraving. Then of course the lead by itself can't take the speed and vaporizes.

 

[cohunt]

Exactly the point I was trying to make.....now, does the heat/ friction from speed cause the jacket to get hot enough to make the lead liquefy and become loose? I say no.....it's the rotational forces from the high twist rates.......which really makes the jacket come apart at the weak spots from engraving. Then of course the lead by itself can't take the speed and vaporizes.

Then why don't non-jacketed lead bullets just vaporize or melt when shot?