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Old September 9, 2008, 02:37 PM   #26
fourdogs
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Hi Jim,

Actually I've shot many rounds of various calibers into steel plates as thick as 1". Not withstanding my 50 BMG, the other calibers wouldn't penetrate but would make huge craters with lots of neat stuff going on. The last time I shot into a thick steel plate was with my Swift. I only got back about 40' and shot a round approaching 4000 fps ( don't try this ) The bullet hit the steel, and then I noticed something immediately flying back at me, striking me in the lip. My lip was bleeding, turned black and blue.....and hurt like hell. Turns out ( you guessed it ) the bullet hit the plate and there was so much energy it bounced back and struck me. That was a good lesson, a very good lesson.

I for one am interested in your experiment with the seven rounds. Can you explain why the rounds all came out ? What was the secret that you knew before you shot it ? Needless to say, you must have know the outcome before firing the gun.....or did you.
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Old September 10, 2008, 07:44 AM   #27
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First thing, purposely putting an obstruction in a barrel and firing it is not only extremely dangerous but extremely stupid unless it's being done in a fully controlled and contained test facility.

Yes, Jim, physics does play a roll in all of this but not in the manner you are suggesting. A bullet encountering an obstruction in the bore is completely different than a bullet encountering an obstruction to its flight path outside of the bore.

Inside the bore, the bullet is contained by the bore, this is what allows softer bullets to be obtruded by the sudden pressure rise to fill the bore completely, the bullet obtrudes only until it is fully contained by the bore or until it has reached its maximum allowable deformation limit. Thus is why a bore with a loose or tight spot will often shoot well with soft-cast bullets but will be inaccurate with jacketed or hard-cast bullets - the softer the bullet, the more readily it will conform to the changing diameter of the bore preventing gas-cutting of the bullet and/or bore.

Because the bullet is contained by the bore, when it reaches an obstruction, the bullet will deform only to the point the bore will allow it to reach, once the maximum deformation has been reached velocity is rapidly lost - the rapid loss of velocity is what causes the rapid rise in pressure behind the projectile - it is the pressure rise that destroys the barrel if the yield strength of the of the barrel is exceeded. Barrels can only stretch so far and if you have enough gas volume and pressure to exceed the amount that the barrel can contain, the barrel is going to fail. If you could make the containment (barrel) strong enough, one of three things will happen, either the projectile and obstruction will be ejected from the muzzle, the gas pressure will be contained or vent slowly through leakage or it'll find the weakest point and vent catastrophically.

Because the projectile is contained in the bore, it will not be subject to the same amount of energy transition into heat as when it's deformed outside of the bore. Yes, there will be some energy transition into heat but nowhere near enough to liquefy the bullet let alone the bore with a considerably higher melting point. Barrel failures caused by an obstruction are caused by pressure because the amount of heat generated by the energy transfer is both too small and too slow to be of any consequence.

When a projectile encounters an obstruction outside the bore, such as a steel plate, there is no longer any containment of the bullet or obstruction material thus allowing both to be subjected to deformation. With the exception of certain extremely high velocity and specially constructed projectiles, actual "liquid" deformation is NOT what happens. In the case of common expanding jacketed or all-lead bullet, what happens is called "plasticized" deformation or flow. While the results may have the visual appearance of liquefied flow, what you're seeing is the results of cold plasticized transfer. Yes, there is what seems to be a large amount of heat generated but in reality the amount of energy transformed into heat is insufficient to cause completely melting of the lead let alone the copper jacket or steel. The spatters of lead attached to adjacent areas/objects result from cold mechanical transfer - there is heat involved but not in sufficient amounts to cause an actual bonding like happens with a solder joint but it is rather a mechanical attachment. Yes, it may have the appearance of liquid flow but it is not a liquid flow but a plastic flow where the metal is fully deformed but at a temperature below its melting point. Even when you do get a deep crater or complete penetration of the steel plate, the flow of the steel results from mechanical deformation not melting of the alloy.

Since Nick brought up localized ringing, I'll go a little further into that too because there are two causes of ringing - One is caused by rapid pressure rises resulting by the bullet intermittently stopping and the other is caused by uneven combustion of the powder or what's known as "SPS" (Secondary Pressure Spike". Ringing in or around the chamber is often caused by the bullet being ejected fully or partially from the case by the ignition of the primer, the bullet remains in its new position until the powder burn then builds enough pressure to start the bullet moving again. The increased volume of powder burn area caused by the movement of the bullet allows the powder ignition to happen in a localized area often resulting in a ring at the point of ignition, in other cases the excessive pressure rise caused by the stoppage of the bullet the weakest/thinnest point of the containment will suffer permanent deformation but not to the point of catastrophic failure. Ringing caused by SPS can happen at any point in the bore and bores subjected to repeated SPS conditions will often have multiple rings along most or all of its length - this is often referred to as "wash-boarding" because bores that are severely damaged by SPS will have the appearance of a rippled wash-board.
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Old September 10, 2008, 09:58 AM   #28
brickeyee
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"Well, maybe the other folks would like to explain how that steel flowed backward from the bullet strike since they say there was no heat involved. And where those molten lead drops come from when a .22 bullet strikes a rock since they say there is no heat involved. Actually, you get an even more impressive "splash" when the bullet doesn't penetrate, so all its energy is converted to that heat that doesn't exist. Try a 1/2" or 3/4" cold rolled steel plate instead of a 5/16"."

Plastic deformation.
You do not need to invoke heat at all.

Go smack a bullet with a hammer.
Now smack a piece of wood.

Both will show plastic deformation, and we know that would would burn if heat was involved.

At very high pressures even metal exhibits plastic flow like a very viscous material.

Tension demonstrations are a lot easier (and safer).
A steel rod in a tester will exhibit stretching and a slow reduction in diameter until the are cross section is reduced leading to catastrophic failure by fracturing.
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Old September 10, 2008, 12:27 PM   #29
Hammer1
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Ringing barrel refers to shooting a 55-gallon steel drum and having it sound like a church bell.

By hanging the steel drums from different length chains and springs and having different materials and different amounts of those materials in the drums the notes of the drums (bells) can be changed.

By combining different drums at different distances and different guns and different ammo you can play Dixie.

Yankees can play The Battle Hymn of the Republic, but they'll likely be off-key.

Of course in Texas they will play either The Yellow Rose of Texas or The Red River Valley. But it takes practice.

.
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Old September 10, 2008, 01:32 PM   #30
James K
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Well, all I can say is to take a physics course and learn about conservation of energy. Then explain why that mechanical deformation takes the form of round globules of lead or steel (just like solidified droplets) if there is no heat involved.

Also, why would a barrel expand from pressure at the base of a stopped bullet when it doesn't expand from the same pressure behind a bullet that is moving. (Actually, it does, but the expansion is so small as to be negligible.)

Also, note that as a general rule, mentioned in conjunction with the 9/11 building collapse, is that heat reduces the strength of steel by one half or more. So a barrel that is 1/4" thick becomes effectively 1/8" if heated. By that non-existent heat from that non-existent kinetic energy.


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Old September 10, 2008, 03:15 PM   #31
FL-Flinter
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Show me the proof where you can raise the temperature of a barrel in less than 1/7500 of a second (roughly the time it takes the pressure to blow the barrel) from say 75°F to 2150°F because once you clue me in on that, I'll be retired about 72 hours later as very rich man!
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Old September 10, 2008, 04:28 PM   #32
Hawg
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I shoot a lot of steel plates and I never noticed any melted looking globules. All I see is a flat disc on the ground and a lot of lead smears on the steel.
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Old September 10, 2008, 04:54 PM   #33
dutchy
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Guys,

You got my ears ringing, not to mention the old grey matter in between.
Too bad I do not have the time to study it all.
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Old September 10, 2008, 06:10 PM   #34
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FYI

Quote:
While there are still HEAT rounds (High Energy Anti Tank), the 'state of the art' is a 8 pound depleted uranium (DU) dart.
Early anti tank rounds were solid shot (steel), which would penetrate the relatively thin armor of the early tanks. As the armor got thicker (and hardened), the velocity of the AP shot was increased to defeat the armor. Eventually a point was reached where the AP shot was moving fast enough to shatter against the armor instead of penetrating.

The solution to this was to put a hardened "cap" on the AP shell. Thus, AP became APC (armor piercing capped). As the gun/armor race continued, we eventually reached the point of APCBC rounds (armor piercing capped ballistic capped). And even these had a maximum amount of armor steel that could be penetrated at a given range. The very thick (6"+) frontal armor of late WWII German tanks was proof against many of these rounds, even at point blank range for some Allied tank guns.

At the same time as advances in AP shot were being developed, the HEAT round was also developed. High Explosive Anti Tank (HEAT) rounds used the shaped charge principle. Rather than using kenetic energy to penetrate the tank armor, the HEAT (at one time also known as the "squash head) round strikes the armor, deforms (squashes) into the shape needed for the shaped charge effect, then the explosive detonates, and the shaped charge effect focuses the explosive force into a small area, which "burns" through the armor. HEAT rounds are low velocity (high velocity is both not needed, and actually reduces the effectiveness of the shaped charge warhead), and because of the low velocity can be effectivly fired from light weight weapons like the Bazooka, the German Panzerfaust, and the Soviet RPG, as well as being fired through conventional tank guns. HEAT rounds can be made to penetrate any thickness of armor that a tank can carry.

The Germans quickly recognised a defense against HEAT rounds, thin metal sheets (5mm) spaced some distance away from the main armor of the tank. Since the HEAT round needs a fixed distance to focus the explosive, these "schurtzen" (skirts) would detonate the HEAT rounds too far out from the hull for them to penetrate the armor. The final versions of the schurtzen weren't even plates, but a heavy gauge metal mesh, which worked just as well. Some Soviet tanks had metal bedspring frames welded to their outsides to get the same protection from the German HEAT rounds.

Today, tanks obtain the same protection from HEAT rounds by using "reactive armor", blocks of explosive attached to the outside of the armor, which explode when hit, disrupting the shaped charge, and preventing it from burning through the armor.

AS mentioned, state of the art today is the DU sabot round. Depleated Uranium is used because it is incredibly dense. Denser than tungsten, ro anything else readily usable. The round is a subcaliber "dart" fired in a sabot from a large bore gun (105/120mm), at very high velocity (5,000fps+). The APFSDS round (Armor Piercing Fin Stabilized Discarding Sabot) relies on kenetic energy (very high) focused in a small area to punch through armor, and it has the added benefit that the Uranium is pyrophoric, and is ignited as it penetrates the armor, destroying the enemy tank, normally with a single shot. They have the nickname "silver bullets" because they kill the werwolves DRT!

As to whether it is heat or "cold plasticity" that causes steel to flow under impact, or barrel obstructions, I can't say, not being as highly educated as some folks. All I can say is that the steel certainly looks like it was melted!
Quote:
I shoot a lot of steel plates and I never noticed any melted looking globules. All I see is a flat disc on the ground and a lot of lead smears on the steel.
Hawg, if you shoot steel plates with high velocity rifles, you will see the steel plates crater, looking very much like they were melted.

I don't know what they teach nowdays, but back when I was in school they taught that pressure=heat and heat=pressure in general terms. Somebody mentioned torsion and how the steel reduced diameter before it broke. What they didn't mention was how a torsion breakage also generates a lot of heat.

Call it what you want, under high pressure, steel (and lots of other materials) act like liquid. And they get hot too!
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Old September 11, 2008, 10:43 AM   #35
brickeyee
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Quote:
What they didn't mention was how a torsion breakage also generates a lot of heat.
It depends on how fast the test is run.

They are normally run slow enough to prevent any heating from affecting the results since you are most often looking for static loading results.

Heating affects would also distort the test results in a non-predictable way.
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