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IraqVet2003
Advanced Member
USA
1206 Posts |
 Posted - Nov 01 2009 : 01:29:07
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| Sorry but that has to be a bit disconcerting even with alot of dirt in front of you, the idea of having bullets going over my head was never appealing and even less when it has actually happened. Vet |
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Mike70560
Junior Member
USA
73 Posts |
Posted - Nov 01 2009 : 07:41:12
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Accidents are far and few between. I was at Camp Perry I believe in 1997 when a bullet hit a stair on the center of Viali range, ricocheted and hit a Marine in the jaw. the stairs came down.
The president of the Louisiana Shooter Association was hit by a bullet because the steel part of the target carrier was higher than the berm.
I bet both of those guys will say the bullet was HOT. |
Mike |
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brian 0714
Junior Member
43 Posts |
Posted - Nov 01 2009 : 10:40:31
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I know a 50 m2 will ignite a gas can,and I can tell you shrapnel,burns like mad when you are hit with it(personal experience
on that one).Still have two pieces that go everywhere with me(in my back).I would think with air friction,why couldnt it get hot?I would think that it must heat up from the air friction.A projectile passes through something so fast that I doubt you will see burned hair.
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Wolfgang
Advanced Member
1553 Posts |
Posted - Nov 01 2009 : 23:16:12
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The bulk of the heat in the barrel comes from friction including the friction caused by movement of the iron components caused by the pressure rise & fall as well as the vibration and of course from the burning powder. The bulk of the heat in the bullet comes from the friction of it in the bore, very little comes from the burning powder because of the small exposure area and extremely limited exposure time.
Bullets are also heated by friction with the air, first when the front of the bullet is compressing the air in the bore, some of that heat also goes into the barrel. I haven't gone to the point of doing the calculations myself but according to a fellow who has, a typical spitzer up to 0.750" in length will rise to approximated 520°F if it has a sustained velocity of 3950 fps for a duration of about 700 yards - key here is "sustained velocity" meaning it does not slow down over the distance traveled but we know for fact that the bullet is slowing down from the time it clears the muzzle so the calculation is not correct for an actual bullet but it gives you an idea of what it requires to obtain a higher temperature.
Now, different shaped bullets have differing interactions with the air proportional to their velocity. Depending on the exact shape of the nose, bullets moving at supersonic velocity tend to primarily fly within a vacuum as the air is split by the nose of the bullet however there is friction at the nose and at base and the heat created in these areas quickly mitigates throughout the entire bullet. Highly pointed bullets do not necessarily provide the optimum air-splitting capability, windtunnel testing has shown that somewhat less than a pointy point, in other words a small meplat, provides better aerodynamics in supersonic flight. In subsonic flight, a larger meplat is actually more desirable but it all has to do with the overall diameter and length of the bullet. For all practical purposes, the flight stability and velocity loss of any bullet flying at either supersonic or subsonic velocity for the entire duration of the flight is controlled more by the base than the nose.
The following quote and many others similar to it have been posted around the web and no one from Hornady has yet to deny the claims as to its validity especially when some fairly credible people attribute these statements Hornady.
quote:
Hornady tech's state 2600 FPS will melt soft lead tips in flight. They also said V-Max bullet tips are not plastic, they are made of a polymer product, higher melting point than lead.
But, then again, some gun rag writers continue to claim that jackets were put on bullets because lead bullets will melt at speeds above 2,000 fps. Well, to each his own but we've chronied cast lead bullets trucking along in excess of 2,600 fps and they managed to hit the backstop pretty damn hard giving a good indication they didn't "melt"... Then there comes the old gunshop gossip about the .22-250 & .220 Swift bullets that melted down in flight turning into a puff of smoke at some point down range. No disputing the fact that these bullets do occasionally come apart but it's not from "melting", it's from the combination of thin jacket and excessive rotational force ripping the bullet apart. There's only so much force a bullet can take and launching a thin jacket bullet that's already severely damaged by the rifling at 4100 fps from a 1:9 twist bore has it turning at 328,000 rpm and yep, it can get ripped apart from the rotational force. Once you get over about 155,000 rpm, the rotational force is getting excessive.
As for the polymer tip having a higher melting point that lead ... fat chance as even the high-temp polymers containing 40% carbon solids have a melting point around 590°F yet the melting point of the almost pure lead bullet core is 622°F
While we're at this, let's just dispel the other myth about the lead tips melting at velocities over 2.600 rpm. Quite a number of people, including the alleged "experts" claim
quote:
"I can see the trail of melted lead droplets coming off as the bullet goes downrange if the light is right."
Again, it's a yes & no to the statement ... yes, you can see the bullet trail if the light conditions are right and no, it's not melted lead coming off that you're seeing, it's the condensed water vapor following the supersonic channel. Anyone who has watched an airshow will note seeing little white trails occasionally coming off wingtips, that's the same water vapor condensation only in larger form having a longer duration so it's much easier to see. |
 Carry the battle to them. Don't let them bring it to you. Put them on the defensive and don't ever apologize for anything."
Harry S. Truman
mark@fire-iron.biz
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fishstan2
Advanced Member
USA
1601 Posts |
Posted - Nov 02 2009 : 03:39:15
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AvyDriver, I am jealous. 3000 rounds a week, I wish. I bet you enjoy your job though. Stan |
WILLIAMS, STANLEY W.
SGM U.S. ARMY
CAMP TAJI IRAQ
"SHOOT EM FROM LONG" RANGE" |
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edward5759
Average Member
133 Posts |
Posted - Nov 02 2009 : 10:28:11
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Air friction, or air drag, is an example of fluid friction. Unlike the standard model of surface friction, such friction forces are velocity dependent. The velocity dependence may be very complicated, and only special cases can be treated analytically. At very low speeds for small particles, air resistance is approximately proportional to velocity
where the negative sign implies that it is always directly opposite the velocity. For higher velocites and larger objects the frictional drag is approximately proportional to the square of the velocity:
ed
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