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

[Russel Nash]

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

[chief3]

Yes they do. I have seen plenty of evidence from both high speed cameras and recovered boolits.
Also, the minnie bullet of Civil War fame wpuld never have worked without obturation.

[Russel Nash]

Man! That was quick!

I might have to go back and add a third option. Yeah, I already knew about the Minie balls and their design.

But you didn't vote yet! Be sure to vote.

[Russel Nash]

chief3 wrote:

I have seen plenty of evidence from both high speed cameras and recovered boolits.

Do you have links to any of these videos and/or pics of the recovered boolits?

[Russel Nash]

Please, people, just vote. Let the poll kinda run it's course for a while and then you can chime in later with your opinions. Thanks!

[454PB]

I had to vote no.

They can only obturate if one of the critical measurements isn't correct.

[Marlin Hunter]

yes to a point. you have high pressure applied to the base of a bullet and a little more than atmospheric pressure, combined with compression of the air during acceleration, at the front of the bullet. the rear wants to go faster than the front, so it would distort or compress the lead a little to make it expand. I don't think it would expand to fill in an air gap between the barrel and a smaller diameter boolit, but it would cause greater pressure and sealing of a well fitting boolit.

I might have the wrong definition of Obturate.

[Marlin Hunter]

Please, people, just vote. Let the poll kinda run it's course for a while and then you can chime in later with your opinions. Thanks!

oops

I started typing before you posted that.

[Edubya]

When that boolit hits the lands there (if not the forcing cone) is a bit of friction. It only seems reasonable that it would obturate then, if not before.
EW

[Russel Nash]

Marlin Hunter wrote:

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

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.

[felix]

Why do tight necks cause trouble? ... felix

[Springfield]

There is a large difference between compressing and moving material. Hit a bullet with a hammer and tell me it doesn't change shape. Or for that matter, using your reasoning, a bullet sizer couldn't possibly reduce the diameter of a bullet. But we know it does. You are just using the wrong term. "The mechanism by which an undersized soft metal projectile enlarges to fill the barrel is, for hollow-base bullets, due to expansion from gas pressure within the base cavity and, for solid-base bullets, upsetting - the combined shortening and thickening that occurs when a malleable metal object is struck forcibly at one end".

[Russel Nash]

Springfield wrote:

Hit a bullet with a hammer and tell me it doesn't change shape.

I am assuming that you are putting the cast boolit like on a heavy duty steel table or an anvil or out on a concrete sidewalk. And then you are whacking it with a hammer.

If so, then that really isn't an apples to apples comparison in my opinion

Springfield wrote:

"The mechanism by which an undersized soft metal projectile enlarges to fill the barrel is, for hollow-base bullets, due to expansion from gas pressure within the base cavity and, for solid-base bullets, upsetting - the combined shortening and thickening that occurs when a malleable metal object is struck forcibly at one end".

I couldn't get all that to fit on the thread's subject line.

[Bullshop]

If boolits didn't obturate a muzzle loader wouldn't work very well.
I sell lot of conicel boolits for ML. I was curious to see how hard a boolit would be small enough in diameter to load easily but still obturate enough to give good accuracy.
A test was undertaken using annealed .451" jacketed bullets loaded on a fairly stiff charge of 777 in a 45 cal in line. Accuracy was excellent and the recovered bullets showed normal engraving proving that they did indeed obturate sufficiently to act the same as a bullet starting out at groove diameter in stead of starting out at bore diameter.
BIC/BS

[Russel Nash]

Hmmn....(sigh)

I guess I should have narrowed down this poll even more so that it EXCLUDED muzzle loaders.

I don't have a muzzleloader. I am not really interested in them. Plus, I already mentioned above that I already knew about the Minie balls.

(sigh)

[462]

I have neither a scientific nor metallurgical background, and never went to college, but, from what I've experienced, Felix is spot on.

[Jim]

Russell, with all due respect, my friend, I think your mind is made up and I don't think anyone is going to change it for you. Having said that, I don't think labaratory proof would convince you of obturation.

[Edubya]

Does a golf ball or a baseball compress? They ain't in a cylinder or being held against a solid barrier. I don't know if it can be explained in simple language and I'm just a simple man, so I'll leave it up to you to make your own decision as I have mine.
EW

[felix]

Gosh, darn, waddya' know! ... felix

[runfiverun]

well that all stopped me from going into the use of 428 boolits in my 430 sized 44-40 bbl.