Obturation of a patched round ball...real or imagined?

[roundball]

I've always wondered what it is like to have zero curiosity about the world we live in and how it works. What say ye?

Spence

Different strokes for different folks I guess Spence...never-the-less, sometimes its enjoyable to just sit back with a fresh bowl of popcorn and watch these threads...see all the human traits come creeping out...highjacking, crawfishing, drifting off course, face saving, introducing "proof" that isn't even about PRBs, and on and on.
The thread title of course is: "Obturation of a patched round ball"
:wink:

 

[Billnpatti]

Ladies and gentlemen, I thank you for your interest and input, pro and con, on this subject. I know that at this point in time, the question is yet to be completely resolved. I am impressed by the amount of technical knowledge possessed by some such as Colorado Clyde, MD and others. I am really impressed by the curiosity and technical abilities of such folks as Pletch and a few others. I even enjoy the pragmatism of some such as Cynthialee who simply ask the question Why bother? In many ways, such questions are like the ones asked about the work of such people as astrophysicists. I have on more than one occasion asked why they spend so much money studying things that we can neither do anything with nor do anything about. There are many things that stir my natural curiosity to want to know about them and better understand them. Most of the time, the things that I study are things that have practical implications. Occasionally, it is just for the knowledge. I am afraid that the question at hand falls more into the category of the latter. Even so, we are blessed by having such people as Spence10 who ask, in essence, Why not? Curiosity is a wonderful thing. Knowing how to apply that curiosity to produce practical or pure knowledge is a wonderful gift. To all who have made a contribution to this thread, I say thank you for your input. And, Pletch, for your amazing work, unbridled curiosity and the ability to wrest knowledge from that curiosity, I salute you. :hatsoff:

 

[Rifleman1776]

The flattening could have been the result of grossly excessive pressure when loaded.

How do you explain the sprue then???

The balls flatten more in between each other because there is very little contact area there to dissipate the pressure,(this magnifies the pressure) there is also a void where the lead can expand.
The bottom of the bottom ball does not flatten on loading because it is cushioned by the powder and when fired the gas pressure is distributed evenly over the arced surface.
The presence of a sprue indicates that it was not forcefully loaded.

I did say "could have" because none of us really know.
The sprue could have stayed after loading depending on the shape of the jag used to seat. Or the loading pressure was not hard enough to deform the sprue.
The only thing we know is we don't know.

 

[Vaino]

Although I agree w/ most of your post w/ the exception being....."obturation "OF" a patched round ball". "OF" should be replaced w/ "BY". Not being critical, but the definition of "obturate" is to close, seal off or stop up a bore so there's zero gas blow by.

As far as being inquisitive....I've been that all of my working life and still am, but only about things that have some importance.

Whether a RB increases in dia or not when fired isn't of major importance in "obturating" the bore....the patch is responsible for doing this. So if it is a fact that a RB does increase its dia when fired, the amount of increase is small and nearly undetectable.

The most difficult areas of a bore to obturate are the grooves...the areas that the RB and patch do completely seal off are the lands and a small increase of the RB's dia just slightly increases the seal.

I suspect that if many shooters would calculate the patch thickness req'd for the actual bore and groove dias and the RB dia being used, they'd find that the patch thickness isn't sufficient to seal off the grooves.

It would seem that w/ radius groove rifling the patch can more readily seal off the grooves because the grooves don't have sharp corners as w/ flat bottom rifling.

When starting to shoot and hunt w/ MLers, I developed very accurate and efficient loads because I took the time to calculate a patch thickness that sealed off the grooves. Whether or not a RB increased in dia was not considered because from a practical standpoint, it didn't matter. So...how many of you consider a RB's increase in dia or not when fired when determining a suitable patch thickness for a RB's dia?.....Fred

 

[azmntman]

I've always wondered what it is like to have zero curiosity about the world we live in and how it works. What say ye?

Spence

Ya got me :surrender: . I just guess I am satisfied on many aspects to know that it works. The meaningless(?) results (a tiny change in shape of a ball we likely will never see again and will fly true regardless) don't matter, to me at least. I guess it could be interesting to know but as for us simpletons I guess we have not the need to find out (or the time for me anyway). Not saying others with the mind and time and drive should not discuss or experiment though, (i'm still reading aint I) :grin:

 

[Billnpatti]

Although I agree w/ most of your post w/ the exception being....."obturation "OF" a patched round ball". "OF" should be replaced w/ "BY". Not being critical, but the definition of "obturate" is to close, seal off or stop up a bore so there's zero gas blow by.

Thank you, Fred. "By" is grammatically correct. In using the word "Of", I likely gave the incorrect impression of my subject. I was talking about the sealing off of the bore as the result of deformation of the ball due to the either the gas pressure or acceleration or both aside from any effect of the patch or lube. Perhaps my subject would have been better served had I used the term "deformation" rather than obturation. However, I used the word obturation because that is the word that was being used by those who were posting on another thread. I was addressing that subject, so I used that term.

However, in the end, poor grammar is poor grammar.

 

[coloradoclyde]

I've always wondered what it is like to have zero curiosity about the world we live in and how it works. What say ye?

Spence

I imagine that is what it would be like to be a machine....No imagination..no consciousness...no creativity....to be taught or programmed but never to learn....existing only to perform repeated tasks for that which has created you until such time as you are scrapped and replaced by another machine.

Not my idea of living.

 

[Vaino]

And you're a philosopher too? You're treading on subjects that really aren't at all in "your realm". Your statements as to how people should behave doesn't help in this discussion and only shows...well I'm not qualified, as are you, and we're both certainly not qualified to ascertain how people think and the reasons they think as they do . This discussion is really about "who wins" and ego and the facts are ignored... and you're a contributor to this "winning above all"

I don't think you read other's opposing viewpoints completely or don't digest the meanings of opposing views....this is quite evident in your responses. Seeing this discussion has deteriorated into "winning above all" and for what little contribution I've made to this "discussion". I take partial blame, for it has deteriorated into a controversial but minor subject that from the onset was doomed to be "what it has become".

Up till now I've just offered what I perceive as technical aspects of internal ballistics in a MLing BBl....what you've offered were irrelevant info and personal biases.

This topic should be "locked" before the "fireworks" really start......Fred

 

[coloradoclyde]

Fred,
I think you have read way more into my comments than was intended. :v

 

[Vaino]

Please re-read your previous post about a "machine"...that really pertains to people that you evidently disagree with. You don't have to reply to this post....if you do, I'll read it, but won't respond.... :dead: ..At 83 I'm more interested in discussions about more practical things....Fred

 

[coloradoclyde]

At 83 I'm more interested in discussions about more practical things....Fred

Ok! Great! let's get back to the discussion then. :thumbsup:

 

[Larry Pletcher]

I have wondered about the deformation of a ball for quite a while and am not likely to give up just yet. It doesn't bother me that the result will not affect the way we handle our guns. It would bother me if I could not find a solution. One of my science teachers never gave a direct answer. He would say, "Can you design an experiment to find the answer?" So, now you know where I'm coming from.

After doing a photograph of a ball at 1000 ft/sec, the method is there except for the fast flash. Below is a ball pic just separated from the patch. Another pic shows the physical setup.





The blur in the ball pic will be solved by the short duration flash. This pic was at or under 1000fps. I believe the method will work with the proper equipment. I have seen projectiles at 2800 fps stopped well enough to have rifling measured. So, this gives you the method in the madness.
Regards,
Pletch

 

[Billnpatti]

Yeah, Fred, I did poorly word my original posting on this subject. In re-reading it, I wish I had done a better job of wording it. All along, the poster on the original posting on another thread used the word "obturate". I knew from the context that he meant "deform" and that is what I was talking about. Well, that is the second mistake I have made in the last 10......maybe 20 years. Yeah, right. :rotf:

 

[coloradoclyde]

For those who have yet to read the book.
There is more than one way to demonstrate obturation or upset of a bullet.

One way was to load a bore diameter bullet. upon recovering that fired bullet rifling grooves were visible on the bullet. Proof that firing obturated or upset the bullet to fill the grooves.

Subsequent testing revealed that as the BHN or hardnes of the bullet alloy used increased, obturation or upset decreased and no rifling marks were visible.

The same test principals have been identified and understood as relating to barrel wear in military artillery guns and tests.

 

[coloradoclyde]

"Can you design an experiment to find the answer?"

I think that's a great perspective Pletch

If done fully your experiments should be able to produce both results. obturation and non-obturation. By changing the variables both can be achieved.

I look forward to your results. :hatsoff:

 

[M. De Land]

A couple of thoughts concerning obturation and bore seal.
The powder column does not burn instantaneously but progresses as the ball moves up bore so the patch has no need to seal in the beginning of the conflagration. The powder compression it self at the base of the patched ball is sealing the bore before it burns.
Obturation has plenty of time to occur before this portion of the powder column burns.
Dr Mann proved this in his testing with progressively shorter barrel lengths.
I believe he was using bullets and not balls which produce more efficiency (faster) burn.
Snow bullets are one of the best ways to capture projectiles as they very often are as close to the same form as when in flight as can be had.
The reason of course is snow is the least dense of any other capture medium that is available.
Two things contribute to the stability of the ball in my mind while in flight.
1. rotation inertia
2. obturation parallel at the bullets waist with the imprint of the rifling. I believe this produces a drag stability much like the corner on a bullet base does or fletching on an arrow.
This effect occurs on revolver balls as well when the waist flat is cut by the chamber mouth on the larger diameter ball.
Patched balls are no longer true spheres in flight but are shaped like a revolver ball to one degree or another.

 

[coloradoclyde]

Keep in mind that it is very easy to fire a projectile with no noticeable obturation.

Extremely hard balls like those of wheel weight alloy or those of brass or marble such as Roundball tested will not show signs of obturation. They are too hard or their crystalline structure will not allow it without fracturing and coming apart.

An undersized ball with extra thick patching also will not reveal obturation.

A small powder charge or insufficient force will not overcome the elasticity of the metal and no signs of obturation will be evident.

If you have ever fired a bullet in a modern gun at velocities above 4000 fps and had a bullet explode as it left the barrel or shortly down range....you have experienced extreme centrifugal obturation.

 

[robert reed]

ff
Wow! I only thought that I was becoming a grumpy old man before I joined this forum. I see now that I still have much to learn from the true masters present.

Hey, we all have our buttons! :haha:

I'm gonna clean my rifle now. I've been shooting, don't have time to argue. :surrender:

 

[coloradoclyde]

Snow bullets are one of the best ways to capture projectiles

This is how I first observed obturation, I was a young teen firing unpatched balls from a rifled barrel into a target in front of a snow bank in the back yard. when the now melted the ground was littered with balls. I picked them up and observed.

 

[coloradoclyde]

It takes a lot of gravel to make a smooth road.
:grin: