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Obduration in MLs

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Pletch, are you familiar with the photo of the double-ball load on page 53 of the original Lyman Black Powder Handbook? To me, that seems to remove all question about upset of round balls.

Spence
 
Thanks for all your thoughts. In many cases the logistics bring out the problems. In hours of mulling this over in my mind, I realize that the key is either recovering a pristine ball or bullet for precise measurement, or managing to photograph accurately enough to see differences. Both of these may be tough to do.

First, in trying to recover a ball or bullet, the two most likely ways involve shooting into oiled sawdust as the slug shooters or shooting into water. I haven’t tried either. Whenever I talk with folks who discuss the oil/sawdust box, most say they didn’t try it but heard it worked. My worry is that the recovered bullet is good enough for the slug guys purposes, but maybe not good enough to get precise measurements. I simply don’t know about how accurate one can be with this method.

A friend tried the “shooting into water trick”. He filled a garbage can with water and set the can in his barn. He shot from the hay mow down into the can. The mini ball split the can down the sides from top to bottom in 4 or 5 vertical seems. The only thing holding the can in one piece was the top and bottom. I told him I wanted to be there with a camera for his next try. I think that the mini ball mushroomed up pretty good- too bad for our purposes.)

My thought about water would be to build a tray that would hold large zip lock bags. Filled with water and placed side by side, you might get a recovered bullet or ball that could be measured. If the bullet was too badly mangled, I’m only out a few zip locks.

Dealing with cameras, the tough part is using a flash with a short enough duration not to blur the image. The same setup I used for the ball shedding the patch would work. BTW the ball in the photo was about 2 ft from the muzzle. Details about the process at the following link:

Link


Oh, stopping the ball or bullet can be an issue too. I’ve used a year’s worth of magazines taped together for the patch/ball shot. (A .40 ball at 1000 fps stopped in the July issue of Guns and Ammo IIRC.) A 540 gr bullet is harder to stop I bet!

Take a look at the photo Spence mentioned if you have Lyman. The important part to me is the sides of the bullet. The front of the rear ball is badly flattened, but the ball’s sides appear to have been flattened too. The area in contact with the barrel is flat ”“ as if the ball had a belt. This is the area I would like to measure.
Rather than removing the breech, I mentioned earlier and Riflemen1776 reminded me of it, that we can simply start a ball with patch down the barrel and pull it back out again. This gives us a look at the length of the marks left by the patch and barrel. If we are able to collect a good ball after firing ”“ either with camera or recovery, and compare to the marks before firing, we may have a good case. I think a ball with longer rifling marks demonstrates that obturation took place. With a bullet, any rifling marks that show demonstrate this.

I hope my typing is better this time. I tried to use an ipad yesterday, and my regular keyboard is much better. Often a “the” shows up still.

Again thanks for all the input.

Regards,
Pletch
 
I have always liked that bullet apple photo. I always found the outward flared skin on the entrance interesting as I would not have assumed the photo would have looked like this if I had to guess
 
plastikosmd said:
I have always liked that bullet apple photo. I always found the outward flared skin on the entrance interesting as I would not have assumed the photo would have looked like this if I had to guess

I tried to take one of those once. I ended up with "apple snot" all over the garage. I would love to see the lab where Edgerton worked, based on all the stuff he tried. But I would not like to be teh custodian that took care of it.

Regards,
Pletch
 
I saw a documentary on him years ago. They showed how this photo was taken, along with a card cut in half. He used a microphone as an electronic switch to trigger the flash. He started by setting up the shot, then turned of all light in the room, opened the camera shutter, then took the shot in complete darkness. He would time it by moving the mike closer, or farther away from the gun. The speed of the sound of the gunshot would determine the timing. When the sound hit the mike, it would then trigger the flash (one of his inventions), and hopefully go off at the right time. That one shot took many many tries to get the timing just right. Yeah, you can bet there was apple snot all over the place when they finally got it right. Bill
 
There was a coffee table book published with many of Edgerton's pictures. It was called "Stopping Time". There are many outstanding pics. The apple picture goes with a lecture Edgerton's called "How We Make Applesause at MIT".

Regards,
Pletch
 
I just got off the phone with my friend Rick, who did the garbage can shot. He said the Minnie ball was too damaged for our purposes. he had better luck with sand.
regards,
Pletch
 
Even if you recover the fired roundball you won't be able to tell if the depth of the cloth weave and rifling marks on the ball were caused by the ball expanding or they are simply the results from loading a tight fitting ball/patch unless you debreach the barrel and ram a lot of patched roundballs thru the bore.

After doing this you will then have a baseline to work from when you make your comparisons.
 
I have to think that if stopping the bullet flattens the nose, that will result in "obturation" far greater than anything that happens in the barrel, especially for a round ball. When the nose flattens, the displaced lead has to go somewhere. If obturation occurs due to the explosion of the powder, imagine how much obturation will occur with a sudden stop. The only ball I ever recovered from a deer obturated from .530 to about .978! :rotf:

I kinda wonder too if forces are great enough to obturate the bullet in the bore and leave patch weave marks on the sides of the bullet, howcum there is no weave marking on the back of the bullet. Seems as though that explosion would cause the patch to indent pretty good, especially since the "ideal" recovered patches are still intact in the middle.
 
BrownBear said:
I have to think that if stopping the bullet flattens the nose, that will result in "obturation" far greater than anything that happens in the barrel, especially for a round ball. When the nose flattens, the displaced lead has to go somewhere. If obturation occurs due to the explosion of the powder, imagine how much obturation will occur with a sudden stop. The only ball I ever recovered from a deer obturated from .530 to about .978! :rotf:

I kinda wonder too if forces are great enough to obturate the bullet in the bore and leave patch weave marks on the sides of the bullet, howcum there is no weave marking on the back of the bullet. Seems as though that explosion would cause the patch to indent pretty good, especially since the "ideal" recovered patches are still intact in the middle.

There is enough compression between the lands and the ball for impressions to be visible, but it would take a microscope to visualize impressions made from the expanding gasses. As the explosion takes place, the ball is expanding outward, placing "x" pressure psi against a soft lead ball. The steel barrel is not giving and further receiving pressure as the ball and gass is attempting to expand. The ball is in motion at the same time, attempting to relieve the pressure. This would be one reason one wouldn't see patch marks on the trailing surface.
 
As you can see the details are the problem.

Zonie,
I was hoping that I could solve the problem you mention by loading a ball with a long piece of patch material. After it was well into the rifling, I'd pull it back out. My hope would be that I'd get the same ball that way as I would if I pushed the ball completely through the unbreeched barrel. Another possibility would be to dry ball and push the ball back out with CO2. I could unbreech a barrel, but would rather not.

Brown Bear,
You're right about the front of the ball. I would not try to use it for measuring. To be successful we'd have to look at the sides of teh ball where it contacted teh barrel.

FL 62,
I agree that teh cloth marks on teh ball won't become deeper as a result of firing. I'm hoping that the marks will lengthen. If the marks are longer, it will indicate that a wider "belt" of the ball contacted the barrel. That would be evidence of obturation IMHO.

As you can guess, the idea of getting a good photo of the side of the ball or bullet becomes more and more appealing as you look at all these problems. I have a much better lens now, with the ability to fill the view finder with a stamp - plenty close enough if ball ends up at the right place at the right time. That presents its string of problems too.

The weather here is too cold to get too excited, and gives me time to think through all this. I want to do a couple of camera tests to see what kinds of things I can get away with.

For instance suppose I short start a .526 and a .535 ball in my .54 with the same patching and then pull them out. Does it make sense to you that the length of cloth marks will be longer on teh .535 than the .526? If that difference can be seen with a camera shot, I might get this to work.
Regards,
Pletch
 
Pletch said:
For instance suppose I short start a .526 and a .535 ball in my .54 with the same patching and then pull them out. Does it make sense to you that the length of cloth marks will be longer on teh .535 than the .526?
Uhmmm, not sure...seems like unless the larger diameter ball actually results in flattening the sides of the ball a bit to engage more patch material...instead of simply compressing the patch material a little more thinner...there would still only be one precise equator around the ball...but I'm no authority on this at all
 
Pletch: this whole topic harkins back to time a few decades ago. I had just received a new .22 from Santa and had to "sight 'er in". Of course, after the obligatory sighting in, we consumed many rounds of "practice" ammo as well. Fast forward to the following spring and finding all the spent bullets on top of the ground, right where the snowdrift was that had been our backstop!!! As i recall they were nearly all in refireable condition. Sumpthin ta think about anyway. Many thanks for all your efforts, Buzzard
 
If the bore is smooth and the material isn't being torn by seating the ball it isn't hard to pull the seated ball back out by the patch. But anymore when I do that I have a small charge of powder in the barrel just in case the patch gives way.

By the way, I just got through polishing the bore of a recut .58. Before polishing it ate patches. Now the ball pulls back out with no problem. It's loading with my weight as all that's needed to seat the ball. And yeah, the lands all leave deep fabric impressions on the ball.
 
Of coarse that photo is easy to take in today's world. With the advent of high speed video, that is. Trying to do it with stills is a trick but pretty straight forward with video. I know the equipment is pricy but I know that it is for rent. Maybe that is a route you could want to take. Video would eliminate most of your problems, if not all.
 
I have used borrowed high speed video cameras with the help of an Olympus tech three different times. The cameras come with their own logistical issues. We have done almost 80 flintlocks at 5000 fps and a flint rifle at 15,000 fps. The major problem is the staggering amount of light required to get anything decent. The last time checked, I could rent one for 1500-2000 a week.

If I can work out the details, we might try to get Olympus to return to Friendship next spring. It would be their third time there. What would be really cool would be for Olympus to come to Friendship, train us, and then Let us rent it for the week. That would be cool!

In the mean time, I guess I'll play with the stuff I have.
Regards,
Pletch
 
the only bullets i can think of that would work at low speeds would be paper patched hex bullets, but, that wouldn't tell you much about obturation and conventional land/groove rifling. as far as stopping bullets, how about ballistics gelatin? make some in several buckets, then line up the unbucketed cylinders and shoot. i'd be good for cold weather, and should stop the bullet unscathed.
 
BrownBear said:
I kinda wonder too if forces are great enough to obturate the bullet in the bore and leave patch weave marks on the sides of the bullet, howcum there is no weave marking on the back of the bullet. Seems as though that explosion would cause the patch to indent pretty good, especially since the "ideal" recovered patches are still intact in the middle.

I always figured it didn't imprint on the back of the ball because the patch is permeable to gas. It's hard to blow through it with just your lung power, but I'm thinking the high pressure of the boom passes right through the cloth. I wonder if something more solid, like textured silicone (if there is such a thing?), were used for a patch, would it leave an imprint of the texture on the back of the ball? Something to ponder while drinking that 3rd beer. :rotf: Bill
 
medic302 said:
the only bullets i can think of that would work at low speeds would be paper patched hex bullets, but, that wouldn't tell you much about obturation and conventional land/groove rifling. as far as stopping bullets, how about ballistics gelatin? make some in several buckets, then line up the unbucketed cylinders and shoot. i'd be good for cold weather, and should stop the bullet unscathed.
I agree. I have to drive my 540 gr pp bullet pretty hard to slice up the patch.

Just for fun, I short started three different sizes of balls for my .54, pulled them back out and measured the cloth marks. Here is a summary:

.526 Marks are faint and short (.152")
.530 Marks easier to see, deeper,longer (.161")
.535 Marks pronounced and longer yet (.208")

BTW the first 2 were easy to pull out. The .535 was pretty hard. The patch used was a strip of pocket drill measuring .019". I wiped the barrel lightly with oil. I spit patched the ball and seated it to the length of my short starter.

This little experiment doesn't necessarily prove anything, but leads me to think that a ball that obturates will leave a longer cloth mark front to back because the bore ride section is now longer. A gut feeling proves nothing so we'll wait and see.
Regards,
Pletch
 
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