Question on ammo...long

[rauchman]

Greetings,

If this is a really stupid question, please forgive me, but I was at my favorite think tank (my favorite stall in the bathroom at work ) and was wondering why high speed rifle bullets don't melt in the air.....or at least there lead cores. I was thinking the frictional forces at say 3000fps or better would be tremendous. Particulary on bullets that don't have a good Ballistic Coefficient. I'm guessing here, but I think the speed of sound is just over 1000 fps. So at better than 3000fps the bullet is cooking at somewhere around 3 x's the speed of sound. Would the heat generated by frictional forces liquify the lead core of a bullet? And if not, why not? I don't know exact temperatures, but I thought lead melts at a relatively low temp. Between the actuall ignition of the powder and frictional forces, is the bullet subjected to enough heat to melt the core. Somehow I don't think this happens, but to me, logically it should. Then I was thinking, if a round was developed that liquifies the core or at least part of the core, once fired, along with a steel jacket for penetration, that this could be an ideal military round. I would think a partial liquid core would retain weight, yet provide great destabilization of the round once it hit a target and generate terrific wounding characteristics. I realize that we don't use massive wounding ammo such as hollowpoints, but the 5.56mm round does fragment upon impact under roughly 200 yards and causes massive wounds.
Just some food for thought!

 

[treeprof]

Maybe in part for the same reason you can quickly pass your hand thru a candle flame or walk on hot coals and not get burned: short duration exposure to the heat source (and the forces of friction in bbl and air)? Bullet jacket also would have to heat first and conduct to core. Prob would take a long, long distance at v. high speed for bullet leading edge to heat that much, and of course they begin to slow quickly.

 

[Larry Ashcraft]

I think treeprof has it right. I checked my ballistic tables once for my 25-06 and I believe the bullet took .13 seconds to go 450 yards. You couldn't melt a bullet in a blast furnace in that time.

 

[Art Eatman]

3,000 ft/sec = "only" 2,045 mph, or roughly Mach 3. The bullet just isn't exposed to atmospheric heating long enough for any melting. Bullets slow down fairly rapidly, so as the time of flight increases, air friction--and thus heating--decreases...

Art

 

[ShaiVong]

Ahh! This is exactly why some MG's are water cooled, right? To chill the bullet before it leaves the barrel, and thus doesnt feel like a hot bird poopie when it strikes the enemy!

Right?

 

[Art Eatman]

Egad, ShaiVong! Your perspicacity is simply whelming, old chap! Whelming, I say!

Rather more under than over, however...

, Art

 

[Jim K]

Well, bullets don't melt in the air, but they can melt if they strike a hard surface. When that happens, the kinetic energy (all those foot pounds) in the moving bullet is converted into heat and the bullet not only melts, but melts the target material as well. A bullet fired into steel will melt a crater into the steel, actually leaving "splash". This freezes quickly, and often looks almost exactly like those high speed photos of a drop into a full glass.

In fact, this is the theory behind armor piercing rifle ammunition; the bullet impact melts the steel and the AP core goes through the molten steel. Since this does not happen in soft material, the effect on soft tissue or body armor is the same for AP bullets as for regular jacketed bullets; the laws and hype about AP bullets are the product of politics and general hatred of guns, not of any rational solution to a problem.

Jim

 

[ShaiVong]

Just incase anybody here doesnt speak Eatmanese

perspicacity

n 1: intelligence manifested by being astute (as in business dealings) [syn: shrewdness, astuteness, perspicaciousness] 2: the capacity to assess situations or circumstances shrewdly and to draw sound conclusions [syn: judgment, judgement, sound judgment, sound judgement]



Dats mee!

 

[Redlg155]

I don't know about melting, but I've heard where ultra fast speed varmint bullets sometimes disintegrate upon leaving the barrel in a "blue" puff of smoke.

I believe it was in a Guns and Ammo article some time ago.

Good Shooting
Red

 

[cdbeaver]

Redlg155:

That's very true. Hornady SX bullets shot rather warmly in my .22-250 never reach the target. Sometimes a comet tail appears on the paper, that's about it.

You can actually see the lead appear to "steam" off the bullet in flight. A dark, cloud-like haze appears downrange.

Hornady cautions--and emphasizes--that SX bullets intended to be shot in guns at less that 3500 fps can and will disintegrate in flight when shot from higher velocity cartridges. They are intended for Hornet, .222 and perhaps .223 velocities.