Obduration in MLs

[necchi]

Your right, pulling the ball introduces a foreign object (screw) that deformates the ball. That displaced lead has to go someplace.

I'm thinking that and oburated ball will be shorter and wider in the bore, not longer.
The cloth marks may not be longer, only deeper or more pronounced.

I can't prove it either but in my mind the ball not only obturates under pressure but it's shape does indeed oscilate under torsion like modes #4 and #8 shown here; http://www.varmintal.com/amode.htm
An awfull lot of stuff happens to both lead and steel in those nano seconds.

 

[CoyoteJoe]

The very best media for stopping a bullet without damage is deep snow. Of course you have to wait for the snow to melt to recover them but those you find will be perfect, provided they hit nothing but snow.
As you mentioned up front the heavy conical bullets certainly do obturate but it does require a certain minimum powder charge to obtain that obturation. It also requires a certain minimum bullet weight for the caliber, in other words a combination of powder charge and bullet sectional density. Roundball gives another example in the column of shotgun pellets. If you pick up some fired plastic shotcups you notice that the pellets near the bottom have embedded into the plastic much more deeply than those nearer the top. The longer the shot column for any given bore size the more pronounced the difference becomes. Pick up some fired .410 wads and you may find some petals of the cup are totally shredded at the bottom, this because the .410 shot column is so long in relation to it's diameter.
As I envision it the base of the bullet or shot column is being squashed between the irresistible force and the immovable object, the powder gas being the irresistible force and the immovable object being the inertial resistance of the projectile itself. Whether or not roundballs do obturate is questionable since they have very low sectional density, thus lack the inertial resistance of an elongated bullet.
For Dr. Franklin Mann's book "The Bullet's Flight" he test fired and recovered many thousands of bullets. Nearly all of the bullets he fired were sized for a slip fit in the bore and depended on obturation to engage the rifling. He demonstrated that obturation can be quite remarkable even with full jacketed bullets.

 

[David W.]

Your right, pulling the ball introduces a foreign object (screw) that deformates the ball. That displaced lead has to go someplace.

I'm thinking that and oburated ball will be shorter and wider in the bore, not longer.
The cloth marks may not be longer, only deeper or more pronounced.

I can't prove it either but in my mind the ball not only obturates under pressure but it's shape does indeed oscilate under torsion like modes #4 and #8 shown here; http://www.varmintal.com/amode.htm
An awfull lot of stuff happens to both lead and steel in those nano seconds.

The oscillation of lead will be very small indeed and extremely short lived. Young's modulus says lead is 2.4. Steel [varies greatly] is around 200.

 

[Larry Pletcher]

Necchi,
I realized as I read your post that I was unclear about pulling the ball. I used the long strip of cloth to pull it. I didn't use a screw. I agree that the screw would ruin the test when it expands the ball. The first 2 I could pull holding the ends of the cloth in one hand and the rifle in the other. The .535 ball was too tight to do that way. I had to tie the cloth to a vice with a cord. I pulled it with two hands on the rifle.

So, nothing was done to the ball except the pressures during loading.

Regards,
Pletch

 

[tg]

For the sake of argueent let's say that a prb does obdurate a very small amount (this would be variable of course due to many factors". Now with that established as a fact, what does it provide us with in the way of usefull information about accuracy, tradjectory or any other factor which it might effect/produce a cause& effect scenario for an average hunter/shooter with typical PRB loads and primnitive iron sights?...or in short balls expand a bit upon powder charge ignition...so what.Not meant to be rude just trying to find the point of the whole issue.

 

[George]

...or in short balls expand a bit upon powder charge ignition...so what.Not meant to be rude just trying to find the point of the whole issue.

tg, some of us find that curiosity about how something works is like an itch that has to be scratched. It doesn't have to have a purpose or do anybody any good, we just have insatiable curiosity about it. Then, there are people who seem to have no curiosity, and that, for me, is one of those things which brings on the itch, big time. :haha:

Spence

 

[Larry Pletcher]

Tg,
I didn't see anything rude in your comment. I've wondered about this idea for years. Probably 10+ years ago Spence and I were on a list where this was argued strenously. Because its easier to argue than prove, we never arrived at any conclusion.

I really don't care whether obturation takes place or not, but as Spence says, it bugs me not to know the answer. It bugs me even more not to be able to find the answer. Whether we find the answer or not won't change ML shooting a bit, I still want to know.

(When kids asked questions in my science class, one of my answers I gave was ,"How could we set up an experiment to find the answer?" Now I'm being hit by the same question I used on the kids.)
Spence, you pretty well hit it.
Regards,
Pletch

 

[paulab]

Everybody.....please read Dr. Franklin Mann's book "the bullet's flight". He experimented with this stuff for 20 years over a hundred years ago. Obturation starts before the bullet even begins to move [with normal powder charges...not squib loads]. His book is profusely illustrated. He compared a soft lead bullet to a lump of putty saying that they both had a lot in common. In my long range muzzleloader, I load 90 grains of Swiss 1 1/2 followed by a bore sized bullet that slides down the bore under the weight of the ramrod....no wad is used. My grease groove bullets are sized .450, bore diameter is .450...groove diameter is .458. Bullets of mine recovered in the sand behind the 1000 yard targets show very well defined rifling marks. Again, the bullet sits on the powder....no wad. If the bullet didn't obturate INSTANTLY, gas blow-by would gas-cut the bullet, cause barrel leading, and wild shooting, none of which happens. If you can deform a round ball when you smack the short starter, what do you think happens when that ball accelerates from zero to 1800 feet per second in 3 or 4 feet? It gets shorter and wider....[obturates]. cheers Paul

 

[David W.]

Everybody.....please read Dr. Franklin Mann's book "the bullet's flight". He experimented with this stuff for 20 years over a hundred years ago. Obturation starts before the bullet even begins to move [with normal powder charges...not squib loads]. His book is profusely illustrated. He compared a soft lead bullet to a lump of putty saying that they both had a lot in common. In my long range muzzleloader, I load 90 grains of Swiss 1 1/2 followed by a bore sized bullet that slides down the bore under the weight of the ramrod....no wad is used. My grease groove bullets are sized .450, bore diameter is .450...groove diameter is .458. Bullets of mine recovered in the sand behind the 1000 yard targets show very well defined rifling marks. Again, the bullet sits on the powder....no wad. If the bullet didn't obturate INSTANTLY, gas blow-by would gas-cut the bullet, cause barrel leading, and wild shooting, none of which happens. If you can deform a round ball when you smack the short starter, what do you think happens when that ball accelerates from zero to 1800 feet per second in 3 or 4 feet? It gets shorter and wider....[obturates]. cheers Paul

I can't argue with that.

 

[Larry Pletcher]

Everybody.....please read Dr. Franklin Mann's book "the bullet's flight". He experimented with this stuff for 20 years over a hundred years ago. Obturation starts before the bullet even begins to move [with normal powder charges...not squib loads]. His book is profusely illustrated. He compared a soft lead bullet to a lump of putty saying that they both had a lot in common. In my long range muzzleloader, I load 90 grains of Swiss 1 1/2 followed by a bore sized bullet that slides down the bore under the weight of the ramrod....no wad is used. My grease groove bullets are sized .450, bore diameter is .450...groove diameter is .458. Bullets of mine recovered in the sand behind the 1000 yard targets show very well defined rifling marks. Again, the bullet sits on the powder....no wad. If the bullet didn't obturate INSTANTLY, gas blow-by would gas-cut the bullet, cause barrel leading, and wild shooting, none of which happens. If you can deform a round ball when you smack the short starter, what do you think happens when that ball accelerates from zero to 1800 feet per second in 3 or 4 feet? It gets shorter and wider....[obturates]. cheers Paul

Hi Paul,
I have read Mann's book and agree with you. In fact he shows photos of bullets that obturated after if left the barrel. I saw hollow based bullets that almost looked like bells.

My reason for the round ball work is to find a way to measure this. When recovering a ball, it would be hard to measure it front to back and make any claims because of deformation on impact. Thia is why I would like to measure the length of a rifling mark to see if it is longer than on a short started (but not fired) ball.

In bullet work, my 540 gr pp bullet is soft lead. With conpetition loads it shreads the patch in long strips, so I know it bumps up. I experienced your comment about burned patches also.(40 gr burns patches; 90 gr shreads them.) In Tevin Tinny's article in Muzzle Blasts (Oct 78)rifling marks extended forward past the cross patching when using soft lead. This part of his bullet left leading in the barrel.

In both of these projectiles I want to play with a couple of methods. Tinny's article explains the sawdust/oil box. I feel I can come close with a close up photo also.

Regarding Mann's work, I don't remember if he experimented with a sawdust box. Do you know? What I remember are the photographs.

Regards,
Pletch

 

[Zonie]

My copy of Dr. Mann's book titled
"THE BULLET'S FLIGHT
THE BALLISTICS OF SMALL ARMS
--------
FRANKLIN W. MANN
MARGIN NOTES BY HARRY M. POPE"

It is the 1980 publication by WOLFE PUBLISHING CO., INC. PRESCOTT, ARIZONA

The margin notes by Pope are as interesting as the book with Pope often disagreeing with his friends conclusions.

In my copy of Dr. Mann's book, page 53 talks about shooting into a snow bank he made at 200 yards because at 100 yards "Soft lead bullets were usually mutilated, more or less..."

On page 59 he speaks of shooting into "Oiled Sawdust".
He said that he tried oiled, wet with water and dry.

The dry sawdust caused extreme mushrooming.
The water wet sawdust caused some mutilation of the nose of the bullet.
The oiled sawdust produced almost no damage to the bullet at all. (ref Fig. 28)

His method of preparing the sawdust is as follows:

"The correct method of preparing is to sift through a No. 12 mesh sieve fine maple or birch sawdust and mix with thin machine oil which will not gum.
The dust takes much oil, and sufficient must be added to thoroughly saturate without dripping; then resift [sic] thru a No. 6 or 4 mesh, and if properly prepared it will not cake but will fall back into the furrow made by a bullet, as coarse dry sand will act,: (PP59-60)

 

[Dphar]

Everybody.....please read Dr. Franklin Mann's book "the bullet's flight". He experimented with this stuff for 20 years over a hundred years ago. Obturation starts before the bullet even begins to move [with normal powder charges...not squib loads]. His book is profusely illustrated. He compared a soft lead bullet to a lump of putty saying that they both had a lot in common. In my long range muzzleloader, I load 90 grains of Swiss 1 1/2 followed by a bore sized bullet that slides down the bore under the weight of the ramrod....no wad is used. My grease groove bullets are sized .450, bore diameter is .450...groove diameter is .458. Bullets of mine recovered in the sand behind the 1000 yard targets show very well defined rifling marks. Again, the bullet sits on the powder....no wad. If the bullet didn't obturate INSTANTLY, gas blow-by would gas-cut the bullet, cause barrel leading, and wild shooting, none of which happens. If you can deform a round ball when you smack the short starter, what do you think happens when that ball accelerates from zero to 1800 feet per second in 3 or 4 feet? It gets shorter and wider....[obturates]. cheers Paul

Mann did not shoot round balls.
Much of his work was with smokeless.
I have never seen any evidence that a ball recovered after firing showed any significant expansion. No indication of patch prints at the grooves for example that are not present in loaded and then pulled ball. So if the typical RB "bumps up" its not more than .001 or .002"

I have used tapered and under sized elongated bullets in a ML and breechloaders with BP. 2.5 to 3 caliber long (or even shorter) 40 and 45 caliber bullets will upset a great deal. In a .456 BORE, not groove, ML barrel a .457 Lyman 457125 will bump up so much that the .450"- bore riding nose will have significant rifling marks all the way to the ogive.
But a 525 gr 45 bullet has a lot more inertia than a 45 RB.

Dan

 

[Larry Pletcher]

Dan, Zonie,
Thanks for your thoughts. I need to borrow Mann again and go through that section. A BPCR shooter on another list told me he though a 12x12x96" box would do well. He'd give me his if we were closer. Anyway I think it's worth the effort.
I don't plan on giving up the photo idea. The Patch/ball shot was at 1000fps. A bullet shedding a pp wouldn't need to travel much faster than that. I want it loaded heavy enough to get a sliced up patch in the photo. That will take some preliminary work to confidently stop the bullet inside. Maybe it would be easier to move all my camera stuff to our range. It takes multiple tripods with cameras, flashes, infrared equipment, etc. I have to think on that.
Regards,
Pletch

 

[ebiggs1]

Olympus high speed video cameras are among the best. The one that you got to try, was it film or digital?

 

[Larry Pletcher]

Olympus high speed video cameras are among the best. The one that you got to try, was it film or digital?

Ebiggs,
The Olympus was a digital. We could just start it and then fire the lock or rifle. Then we'd run it back to the starting point and select the piece we wanted and paste it unto a memory card. That was the method used for all the slow motion video.

However, realized that I have to be careful about terms. In the post above I mentioned patched ball pic and said it was done at 1000 fps. There I should have said the velocity was 1000 feet per second not frames per second. That was a still shot where the ball broke a beam that set off the flash. Works like this:

Shooter ready
Room lights off
Camera shutter open
Shot fired
Ball breaks beam causing
Flash to fire
Camera shutter closed
Lights back on.

Anyway, after this I'll say feet/sec or frames/sec.

Regards,
Pletch

 

[JeffinNZ]

Assuming the powder being burned is 3Fg the pressure generated relative to the nominal velocity of 1000fps in the .40cal will not be at all very high. I doubt it will be enough to cause much if any lead upset.

I have a rather dinky lil .40cal Minie ex a Lyman mould I understand Dixie commissioned in the 1970's. I paper patch it and shoot over 30gr of Swiss 3Fg for 1500fps. Here are before and after projectiles. They upset very nicely.

 

[Zonie]

Although they upset nicely I suspect most of it was due to the hollow bases.

The powder gas will expand the slug from the internal pressure when it fires.

I believe Pletch is looking for evidence that Newtons first law is responsible for some swelling of a round ball as it is shot.

 

[Larry Pletcher]

. . . snipped
I believe Pletch is looking for evidence that Newtons first law is responsible for some swelling of a round ball as it is shot.

Zonie,
You're right. I'm interested in any measurable changes that can be seen after ruling out deforming caused by loading and impact. I either have to recover the ball or bullet with NO impact damage or photograph it in flight before impact.

With the bullet, sources like Mann, Tinny, and others already have substantial evidence showing that bullets "bump up."

With a round ball, no one that I'm aware of has ruled out the loading and impact damage to study changes caused by the firing of the load. The lack of evidence might be a clue that I bit off more than I can chew. I hate to admit that though.

Regards,
Pletch

 

[JeffinNZ]

Maybe it's the HB but then Maxis and REALs slug up also. So do the heels on my .310 Cadel bullets.

 

[ryoung14]

One of my TCs shot Maxis very accurately when loaded ahead of 80 gr. of Pyrodex P. Not so when using RS. Always thought it was because the faster pressure rise force the slug to fill the grooves better.

Then TC told me that using Pyro P to shoot conicals was a No-No.