Do you believe that lead boolits actually obturate (swell up) when fired? Yes or No

[lwknight]

What happend when enriched plutonium is compressed into a denser state? LOL

[John Boy]

Well, looks like the 94.7% who voted Yes that lead bullets obturate have a handle on the tea cup
What I'd like to know is ... why the 6 voted No?
So as the curtain slowly closes on this thread ... "GOOD NIGHT, Mrs. Calabash--wherever you are!"

[Russel Nash]

303 wrote:

Solids and liquids cand be compressed elastically. Solids can be compressed into a higher density sate. Gasses on the other hand need to be contained - that's what is meant by 'compressible'. Metals have properties like ductility, malleability and elasticity. The latter two properties will allow for obturation in a bore. Permanent obturation would be due to malleability.

Thanks for that most cogent and non-smart a$$ey reply.

Maybe a better word instead of obturation should be deformation or "upsetting".

As in it would be possible for a lead projectile to upset or deform but not necessarily obturate the bore. And obviously there are various degrees of obturation.

As far as density goes, it would be kinda difficult to measure at home the density of a fired and recovered bullet versus that of an unfired boolit.

Said another way, I think a fired boolit does not necessarily become more dense.

I think.... (where density = mass/volume)

[runfiverun]

it cannot become more dense as it has no place to get more mass from.
when i said compressed i meant pushed from one direction the front is not moving just yet but the rear is. what happened to the metal if some is moving and some aint it either goes sideways [not compression] or it compresses [swages] maybe it's just squeezing out the air. [and all boolits have some air in them no matter what we think about our casting abilities.]
if we are squeezing out the air we are compressing the alloy in its solid state.
i ain't no scientist it's just how i picture things in my head.
to me compression is squeezing,just like in an internal combustion engine.

[Marlin Hunter]

John 20:29 ... felix

I had to look that up.

This website has many interesting translations of the same bible

http://bible.cc/john/20-29.htm

[Marlin Hunter]

it cannot become more dense as it has no place to get more mass from.

It doesn't have to gain more mass.

Density = Mass/volume

Change either Mass or Volume and the Density changes.

[Green_Canoe]

In my scan of the responses I saw no mention of inertia. Inertia is the key to the bullet upsetting to fill the diameter of the bore.

I doubt anyone would disagree a lead cylinder when placed between the jaws of a vise and compressed between those jaws will get shorter. When the cylinder gets shorter the material is displaced radially causing the cylinder to grow in diameter.

The effect is the same in the barrel of a gun. One jaw of the vise is the pressure caused by the burning gunpowder. The other jaw of the vice is the inertia of the bullet resisting acceleration. The bullet is shortened and the displaced material causes the bullet to grow radially until that growth is stopped by the barrel wall.

This process can be prevented by sellecting a lead alloy that has a high enough compressive strength that the forces imposed by firing the bullet do not exceed the elastic strength of the lead alloy.

[Maven]

"Solids aren't compressible, like a block of steel. So my thoughts are that a cylindrical piece of lead is a solid, and therefore can't compress or be compressible. Unless of course it was surrounded all around by something strong like a steel swaging die and pressed into a particular shape."

A few ideas that I need explained: If solids aren't compressible, how does one explain the prior use of copper/Cu alloy pellets in CUP (pressure) tests of powder and bullet loads? Also, when bullets are swaged, isn't the solid material compressed? I remember Dave Corbin saying essentially that if you can develop enough pressure, you can swage (reform) just about anything (figuratively). Since these are both empirically true, the question to be asked is, "How likely is it that a bullet (solid Pb, Cu, jacketed) WON'T expand (obturate) under given pressure conditions?" Further, shouldn't obturation be proportional to the mass, acceleration and ductility of the projectile?

[Russel Nash]

Green Canue wrote:

In my scan of the responses I saw no mention of inertia. Inertia is the key to the bullet upsetting to fill the diameter of the bore.

I doubt anyone would disagree a lead cylinder when placed between the jaws of a vise and compressed between those jaws will get shorter. When the cylinder gets shorter the material is displaced radially causing the cylinder to grow in diameter.

The effect is the same in the barrel of a gun. One jaw of the vise is the pressure caused by the burning gunpowder. The other jaw of the vice is the inertia of the bullet resisting acceleration. The bullet is shortened and the displaced material causes the bullet to grow radially until that growth is stopped by the barrel wall.

This process can be prevented by sellecting a lead alloy that has a high enough compressive strength that the forces imposed by firing the bullet do not exceed the elastic strength of the lead alloy.

Exactly!

[Russel Nash]

@ Maven....



Ahhh...jeesh...

There is a difference between a gas that is compressible vs. a solid that is better described as malleable or deformible.

[Russel Nash]

FYI....

http://www.chem.purdue.edu/gchelp/li...character.html

[Maven]

What's the difference between compressible solids and malleable and/or deformable ones, or is this merely semantic?
I meant to include this in my earlier post, but forgot: Ken Mollohan (Molly here) wrote in a recent "Fouling Shot," that while CB's obturdate, they don't expand to as great a degree as we think. However, they are solids and they do obturate, if only to a slight degree.

[Russel Nash]

You didn't click on the link, did you?

That was from Purdue University, I think, it is pretty much the norm or standard as far as what liquids, gases, and solids do.

Compressible in my opinion is that the volume changes and consequently so does the density, since you are packing the same amount of mass into less space. As in you probably have an air compressor in your shop or garage. However, I doubt that you have a liquids compressor or a solids compressor too.

A soft lead boolit deforms much like squishing a marshmallow between your thumb and index finger. Its shape changes, but its volume does not.

[lwknight]

I still say that solids are compressable. Try it with plutonium. Ask Hiroshima, Japan about it.

[Frozone]

I still say that solids are compressable. Try it with plutonium. Ask Hiroshima, Japan about it.

Actually it was Nagasaki, they used the Uranium gun bomb on Hiroshima.

Compressiblity implies a change in density and volume (see Boyle's law, although it applies to a gas).
Lead has no change in volume with pressure (at least real world pressure), which is Exactly why it obturates.

Nash: Great troll by the way!!!

[tonyb]

@ Maven....

No.1 I just messed my diaper.

[AriM]

Marlin Hunter wrote:



And that my friends is what brought me to start a poll here.

From my high school and college physics/chemistry classes, there are only four states of matter:

1. gases
2. liquids
3. solids
4. plasma

Also, in those classes, I learned that of the first 3, only the gases are compressible. Liquids are not compressible, and that explains why hydraulic pistons work on something like a crane or a back-hoe. And why they don't use pneumatic rams or pistons for some stuff. Solids aren't compressible, like a block of steel. So my thoughts are that a cylindrical piece of lead is a solid, and therefore can't compress or be compressible. Unless of course it was surrounded all around by something strong like a steel swaging die and pressed into a particular shape.

What I am saying is that with the exception of very soft lead and/or Minie balls, I think lead boolit obturation might just be a myth.

woah woah woah!!! liquids not compressible...??


http://scienceworld.wolfram.com/phys...Equations.html

http://en.wikipedia.org/wiki/Incompressible_flow

please read the content in BOTH links....ALL materials are compressible.....but in standards based equations we must say that they are NOT, so that a number can be plugged in, and a result reached....by the way I voted Yes....it's my opinion, that if a boolit needs to fill a space it will obturate.....if the boolit already fits the space tightly (which is impossible, unless the rifling grooves were pre-molded into the projetile, within a perfect tolerance) then it will elongate...lead is softer than steel and the rapid expansion of gasses and high pressure spike, should cause the projectile to

1. obturate and fill all voids (and shorten)
2. lengthen due to pressure and uneven heating

I suppose this is just fuel for the fire, but this is simple flow dynamics...if you can't figure out the formulas in the links, it's not important....the results and explanations are all that matter....

ALL materials deform and compress/expand according to pressure....ergo heat


this is another example of people thinking that a + b = c, then c must always equal a + b

it's far too simple to say that one of these things is ALWAYS true....it will depend on pressure, temperature, flow, and hardness....and about a zillion variables than NO ONE here is qualified to measure....

[Maven]

Read the link since I didn't see it earlier. However, they do say "not EASILY compressible," which isn't the same as NOT compressible. Another question and an observation, does obturation (of a bullet) necessarily mean a change in volume as well? Will you enlighten me please? As for the observation, what's the point of the Star Trek image? That I just don't get it? Who's being snide (snarky) now?

[BeeMan]

Nash,

To get an appreciation of lead in the solid state flowing under pressure, you need to see the core extrusion presses at a bullet manufacturer. It's all plastic flow when you exceed the yield strength of the material that is being subjected to pressure.

Hornady turns 260 lb billets of lead several inches in diameter and a couple feet long into spools or core material for jacketed bullets. It takes a fair amount of lead to crank out a couple million bullets a day. They cast the 260 lb billets in house - you should also see the casting pots and billet molds.

BeeMan

[felix]

Everything is compressible, Maven. That's how "they" came up with the idea of the "black hole" being a reality. Obviously, it does not mean that a black hole exists for real unless religiously spoken as such. Obturation does not mean a permanent deformation of anything, projectile or container. ... felix