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

[7of7]

Deliverator wrote:



No, it is not.

A lead boolit contained along its length by a steel bore or barrel has no where else to expand to. It can only travel out the bore, in one direction.

A flying bullet striking a steel plate is not really contained by anything.

Here you have adequately stated yourself that there is bullet obturation. Obturation is more a condition of the bore, than the bullet. The bullet expands to completely fill the bore, and the bore becomes obturated. As a result of this obturation, no gas leaks around the bullet, so leading doesn't happen unless the bullet is of sufficient hardness that the pressure will not deform the bullet enough to cause complete obturation of the barrel, so propellent gasses can escape around the bullet melting a microscopic layer of lead only to leave it in the bore.

Bullet obturation is a myth, however, obturation of the bore by the bullet, as a result of expansion of the bullet is not. Obturation is the same as obstruction, you cannot obstruct a bullet, you can obstruct or obturate a bore...

[felix]

Impossible to get a case stuck with an overload if there is no obturation. A stuck case means the barrel/cylinder expanded and collapsed (did not exceed the elastic limit) trapping the case that expanded and DID NOT contract (enough) because the elastic limit of the case WAS exceeded. Tight necks will not let gas escape around the boolit before the boolit expands. Tight necks are what really is desired, especially with boolits, but also provides no escape room for pressure that might be excessive. Loading books cannot be followed for guns having a tight neck, be the gun a pistol or rifle. A tight neck is not a tight cylinder exit hole, but is the area where the boolit resides in the case before firing. ... felix

Yes, obturation is the act of making an obstruction. The projectile expands to perform an obturation. The word obdurate/obduration is something else entirely and has nothing to do with us. "D" versus "T". ... felix

[John Boy]

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.

Russel, you are hypothesizing incorrectly about a subject that has been studied by renowned individuals that were skilled in ballistics going back into the 1800's, Dr Mann being one in the US and many in the UK such as Halford, Metford, Greener and others. And proven by them that obturation of lead bullets is a fact

In current times, you might want to read this short article on the subject by Glen E. Fryxell ... http://www.sixguns.com/crew/obturation.htm

So, why are you trying to disprove a subject that has been studied for decades when you have not done any research on the subject yourself?

Or is this your way of starting a thread just to see how many views and posts you can generate because your statement based on internal ballistics is a indication of stupidity

[JD Yellowhammer]

We can go back further than the 1800's. Check out Sir Isaac Newton, the First Law of Motion, and "inertia." I know which way Newton would vote in this poll....

[Marlin Hunter]

Sounding more and more like a "bait and troll" excercise.

405, in your post #55, you have me listed as the one who made the quote. I did not write that, Russel did. If you go back to post #10 on page 1, you can see that I wrote what was in the quote box, unfortunatly the board sofware does not transfer the quote.

here is what I wrote that russel responded to.

the rear wants to go faster than the front, so it would distort or compress the lead a little to make it expand.

[405]

MarlinJ, Sorry, it was not pointed at your quote. This too is only in response to Mr. Nash's posts/replies throughout the thread. After listing his education I almost got more "snarky" than Bullshop. Decided to just leave it to the imagination about past and recent past "scientific" minds. Even the most basic high school physics class would teach about kinetic energy, inertia, acceleration, momentum, states of matter, compressiblity, etc. Mr. Nash made it a point to cite his education and then got off on the liquid, solid, gas, plasma tangent.... kinda like a scissors, rock, paper level of discussion. As far as internal ballistics and obturation of a "solid" object in a bore (context of this discussion).... of course a solid is NOT compressible nor is a liquid for that matter... but obturation is not about compression... it IS about deformation of a solid "plastic" object... the bullet. With some exceptions, obturation has more to do with inertia and acceleration than with kinetic energy but the ke analogies in other posts are OK and similar enough.

All this reminds me of the movie "Space Cowboys" where the MIT grad, weeny astronaut cites his education yet has some trouble with a concept. Clint Eastwood turns to him and says something like, "maybe you oughta get your money back".

[stubshaft]

MarlinJ,
All this reminds me of the movie "Space Cowboys" where the MIT grad, weeny astronaut cites his education yet has some trouble with a concept. Clint Eastwood turns to him and says something like, "maybe you oughta get your money back".

Very well put 405.

[Russel Nash]

405 wrote:

MarlinJ, Sorry, it was not pointed at your quote. This too is only in response to Mr. Nash's posts/replies throughout the thread. After listing his education I almost got more "snarky" than Bullshop. Decided to just leave it to the imagination about past and recent past "scientific" minds. Even the most basic high school physics class would teach about kinetic energy, inertia, acceleration, momentum, states of matter, compressiblity, etc. Mr. Nash made it a point to cite his education and then got off on the liquid, solid, gas, plasma tangent.... kinda like a scissors, rock, paper level of discussion. As far as internal ballistics and obturation of a "solid" object in a bore (context of this discussion).... of course a solid is NOT compressible nor is a liquid for that matter... but obturation is not about compression... it IS about deformation of a solid "plastic" object... the bullet. With some exceptions, obturation has more to do with inertia and acceleration than with kinetic energy but the ke analogies in other posts are OK and similar enough.

All this reminds me of the movie "Space Cowboys" where the MIT grad, weeny astronaut cites his education yet has some trouble with a concept. Clint Eastwood turns to him and says something like, "maybe you oughta get your money back".

Did I really come in here and cite my educational background as in a "ha ha, my poop don't stink and ya'll are dumber than a box of rocks?"

Did I really put it that way?

If I came across that way, then my apologies. I am sorry.

What we are discussing is a very interesting metallurgical phenomenon that occurs in a split second.

The technology wasn't around in 1909 like it is today to be able to measure chamber pressure and velocity.

If it seemed to you all that I was stuck on the very definition of "compress" or "compression", again, my apologies. Whole scientific discoveries or research are based upon how certain words are operationally defined.

If you will look through this thread here one more time in one of my posts I wrote:

I never did say that lead was NOT malleable.

Which is, in my opinion, different from being compressible.

This thread has been educational in several ways.

I thanks thee for that.

[357maximum]

When I learned about solids/liquids/gases my professor actually had one caveat about compressible liquids.....

His words "liquids are actually slightly compressible, but we will call them un-compressible for the ease of keeping the equations somewhat sane"

I personally feel (no data to back it up...just a gut feeling thing) that some solids are also a teeny tiny bit compressible but the scientific minds of the day are alot better with their delivery of the facts and then arguing the facts/points than I ever will be. For me to do so would be like starting a gunfight with a dull popsicle stick while screaming the earth is flat and some politicians have our best interests at heart.

Doing such a thing would make as much sense as wiping your bottom before you do your bussiness

Seeing as how my personal trolling exercises normally involve a 21ft starcraft islander/ some downriggers and flutter spoons on the great lakes for trout/salmon....we will leave that one alone eh.

Besides as 405 states...we are talking about about deformation not compressibility..............good form 405.

[Marlin Hunter]

What we are discussing is a very interesting metallurgical phenomenon that occurs in a split second.

The technology wasn't around in 1909 like it is today to be able to measure chamber pressure and velocity.

...

This thread has been educational in several ways.

I thanks thee for that.

The two methods of checking chamber pressure work because metal obturates or deforms. The copper crusher is one example, and the piezo electric stress-strain gauge is the other one. To prove a solid can be compresses, take a long pipe or bar, hold it horizontally with only one end being supported. You will notice the bar bends down do to gravity. The bottom half of the bar is under compression and the top half is under tension. Forgings are also proof that solids can be compressed.

[Russel Nash]

Just an FYI...

I remembered back to my time making stained glassed windows.

The very soft lead came has to be stretched before it can used to construct what is essentially a glass jigsaw puzzle.

So... I have kinda changed my mind about the obturation thing, especially with rifle bullets. Esepcially after see'ing John Boy's picture in my other thread.

If I can just stretch lead by hand with a pair of pliers on one end, while the other end is held in a vise, then YEAH! it is now NOT hard for me to imagine that a lead alloy boolit squishes down when being accelerated from zero to 2,000 feet per second plus plus in the distance of about 20 inches.

And for whatever it is worth to you, I did picture the use of copper plates used in shaped charges...say like in the case of the Deutsche bank president's assassination. IIRC, TNT was used as the "propellant" in that instance. IIRC, TNT burns at something like 14,000 feet per second, so the copper plate folded in half very plastic like and flew at about 10,000 feet per second right through the Deutsche bank president's armored car, and killed him. Leaving his two bodyguards and driver without a scratch.

Anywhoo...again, putting something into compression is different than compressing a gas

Those little piezo electric "transducers" wouldn't work if metal didn't contract and expand.

Thanks again for all your replies.

[felix]

John 20:29 ... felix

[wallenba]

With all variables being equal except the BHN, there must logically be a hardness where it stops obturating. Question is, I guess, is it within the sphere of our uses in casting boolits?

[John Boy]

The technology wasn't around in 1909 like it is today to be able to measure chamber pressure and velocity.

Felix, you are so right but in plain English, this guy doesn't know the difference between S*** and Shinola!

Reference Sources:
1813 - Birmingham Gun Barrel Proof House tests
1841 - William Greener book
1841 - Colthurst copper plate tests
1830 era - Hutton and Robins experiments
1878 - Metford article, written for the New York Spirit of the Times
1888 - Halford book
1889 - C&H's Notes on Shooting (shotgun specific)
** Winchester and UMC caliber specific data by calibers, published in their catalogs before 1909
** Cartridges of the World, ALL Obsolete Calibers developed before 1909 - specific data, including published factory loads
And for good measure ...
Greener, Gunnery in 1858: being a treatise on rifles, cannon, and sporting arms

How can it be that these historical sources made specific determinations how to measure chamber pressure and velocity prior to 1909?

So, Mr Nash - You Prove You are Correct and I am Wrong!
Be sure to post it for all to see
Otherwise, put a plug on your statements that don't hold water and start doing your homework before quoting what you deem to be facts

[felix]

Obturation would stop its rapid climb when the static foward resistance of the projectile is broken allowing the projectile to move. Yes, depends on mass (weight), projectile and barrel hardness, and how tight the projectile had already plugged up the barrel. ... felix

Yeah, maybe a better definition of obturate would be "to plug up" rather than "to close up" or is it "down or sideways". I bet the word was defined in Roman times as the methodology of stopping water leaks, be they in boats or aquaducts. ... felix

[hoosierlogger]

[lwknight]

This thread came to the end of its perverbial road. The course has been ran.

[Russel Nash]

Russel Nash (that's me!) wrote:

If I can just stretch lead by hand with a pair of pliers on one end, while the other end is held in a vise, then YEAH! it is now NOT hard for me to imagine that a lead alloy boolit squishes down when being accelerated from zero to 2,000 feet per second plus plus in the distance of about 20 inches.

Thanks for all the courteous replies everybody.

[swheeler]

Thought I would post the definition of the word, obturation as found in a reloading manual, since that is what we do, reload.

OBTURATION; shortening and expansion of a bullet in the bore in proportion to the pressure exerted on it by gas pressure. Enjoy

[303Guy]

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

Also, in those classes, I learned that of the first 3, only the gases are compressible.

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.