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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
is copper jacket spinning around lead core during flight
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<blockquote data-quote="Professor Doolittle" data-source="post: 2277712" data-attributes="member: 118902"><p>Pressure = temperature in a gas. The pressure can't ever lag or lead the heat because they are the same thing, the kinetic energy of the gas molecules. PV=nRT, if you know pressure you know temperature, if you know temperature you know pressure. </p><p> But you bring up an interesting question, how long does it take for 99% of the gunpowder to be burned and where is the bullet located when that point is reached. I would guess the bullet is traveling down the barrel at that point, not yet out. The visible muzzle blast is just decompression after the bullet is out and takes time, but you do see little sparks sometimes that makes me wonder how much gunpowder is still burning or if those sparks are something else such as primer fragments. </p><p> As far as saying it gains more heat in the atmosphere than the barrel I doubt that. My understanding is the bullet gets compressed or deformed into the barrel. That alone will raise the heat. If you could crush a bullet down with a press and instantly feel it it would be very hot. Also copper is one of the best thermal conductors, so before the bullet even starts moving heat is being transferred from inside the cartridge through the copper into the lead. Its being heated while being crammed into the barrel. Then, on top of that, the lands and grooves are forcing an extreme rotational acceleration from the skin of the bullet inward radially which will cause deformation and pressure that also heats up the bullet. I guarantee you the bullet is hotter at the muzzle than at the target. </p><p>Once the bullet leaves the barrel air friction will add heat to the nosecone, lets call it, but also subtract heat from the rest of the bullet by carrying away kinetic energy, meaning the air atoms go away hotter because they touched the bullet. The net total is going to be cooling. I could be wrong if the cooling capacity doesn't have enough time before the bullet lands. It depends on time of flight and which effect is dominant, cooling or heating.</p></blockquote><p></p>
[QUOTE="Professor Doolittle, post: 2277712, member: 118902"] Pressure = temperature in a gas. The pressure can't ever lag or lead the heat because they are the same thing, the kinetic energy of the gas molecules. PV=nRT, if you know pressure you know temperature, if you know temperature you know pressure. But you bring up an interesting question, how long does it take for 99% of the gunpowder to be burned and where is the bullet located when that point is reached. I would guess the bullet is traveling down the barrel at that point, not yet out. The visible muzzle blast is just decompression after the bullet is out and takes time, but you do see little sparks sometimes that makes me wonder how much gunpowder is still burning or if those sparks are something else such as primer fragments. As far as saying it gains more heat in the atmosphere than the barrel I doubt that. My understanding is the bullet gets compressed or deformed into the barrel. That alone will raise the heat. If you could crush a bullet down with a press and instantly feel it it would be very hot. Also copper is one of the best thermal conductors, so before the bullet even starts moving heat is being transferred from inside the cartridge through the copper into the lead. Its being heated while being crammed into the barrel. Then, on top of that, the lands and grooves are forcing an extreme rotational acceleration from the skin of the bullet inward radially which will cause deformation and pressure that also heats up the bullet. I guarantee you the bullet is hotter at the muzzle than at the target. Once the bullet leaves the barrel air friction will add heat to the nosecone, lets call it, but also subtract heat from the rest of the bullet by carrying away kinetic energy, meaning the air atoms go away hotter because they touched the bullet. The net total is going to be cooling. I could be wrong if the cooling capacity doesn't have enough time before the bullet lands. It depends on time of flight and which effect is dominant, cooling or heating. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
is copper jacket spinning around lead core during flight
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