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

[coloradoclyde]

The really sticky question is which will deform more...a cast ball or a swaged ball?

Swaged balls are pre-compressed...they are formed by squeezing. :grin:

 

[Black Jaque Janaviac]

When you screw into the ball to pull it, doesn't that displaced lead force the ball to expand some?

 

[Black Jaque Janaviac]

I realize the photos are not quite roundballs, but I believe this demonstrates a rather extreme amount of obturation.

This is wheelweight alloy caught in snow. You can see there is little nose deformation.

But note how much the grease grooves collapsed, as well as the bevel base, the middle driving band, and the ogive. The overall length has shortened.

None of this is due to loading because this is fired from a suppository gun.

 

[M. De Land]

The test was far from perfect but was a beginning step and taught me a lot about what I had previously only had an idea of.
I did think there would be more obturation on the ball than what I saw and measured but there was enough evidence even with deformation to convince me that is does occur to some extent even on the slow velocity used in the experiment.
I am reasonably sure that a rifle load with the .535 ball would be more revealing than the pistol was but would require a full capture box of saw dust to catch it of about eight feet in length.
The balls made it clear down through the whole column of saw dust in the stove pipe of 34 inches in length and it tracked straight threw the oiled saw dust never once touching the sides.
In charges 30 through 50 grains impacted the paper under neath the stove pipe and bounced back up and was found in the 2 inch styrofoam plug I had in the end of the stove pipe.
It penetrated the column of saw dust, went through the 2 inches of styrofoam, bounced off the newspaper and was stuck in the bottom of the styrofoam plug without penetrating the paper.
I tamped down the saw dust with a stick every three shovels full to compress it a bit in the stove pipe.
The trouble with pool shooting is water surface tension is very hard when shooting straight down and would likely severely deform a ball at impact.
I have seen it done with modern bullets but usually the gun is submersed to avoid the surface tension bullet distortion. Not a very practical solution for muzzle loaders.
I have a eight foot long capture box under the house I started some years ago and never finished. It is made of a foot diameter sona tube for pouring concrete pilings.
The idea was to use my metal detector to find the bullet in the sawdust column and have two hinged doors in the top of the tube for access in digging out the projectile after locating with the metal detector.
I got it pretty well finished with the saw horse stand I made for it but had no permanent place to set it up and shoot through it.
I think the idea is sound but haven't had a chance or location to try it out.
I read once that the oil mix in the saw dust should be such that it can be felt with the bare hand when squeezing a hand full but not enough to run out so it does take quite a bit of oil.
Mine was not mixed this rich but I could see it in the sawdust from the discoloration as I used old motor oil I had saved from my vehicles.
The oil certainly helped in compressing the saw dust in the pipe and provide more resistance to the ball.

 

[M. De Land]

Great pictures and thanks,I too have seen this repeatedly with snow bullets I've picked up.
The trouble with snow though if finding them until spring comes and then one does not know which order they were shot in.
It takes a lot of snow to stop a bullet and it makes them very hard to find, often they impact the ground as well which always deforms them.
It seems to me that saw dust is the most practical capture medium for our purposes.

 

[Larry Pletcher]

if a bullit is forced into rifling does the bullit get longer from being squeesed ??
Whilst we are on deformed bullits ??

The bore-ride length increases. The overall length may not, in fact I expect the overall length to shorten. The unfired PP bullet has no rifling marks on loading, but has marks the full length of the bore-ride section after.

I expect that that in roundball, we will find the rifling marks increasing in length front to back, indicating that the center of the ball has a longer contact with the barrel- that is if we have enough deformation to measure.

Regards,
Pletch

 

[M. De Land]

Larry, after I found that the ball would track straight down the tube I no longer filled the trash can up with the surround saw dust as in the picture to stop it if it exited the stove pipe.
The balls never once touched the wall of the stove pipe and were found in the bottom stuck in the styrofoam after penetrating and bouncing back , sticking in the bottom of the styrofoam.
I'm not sure wither it was the compacted oil saw dust or the paper that deformed the balls.

 

[M. De Land]

I don't know of anyone with a pool up here Bill or even if they did would let me shoot in it.
"Hey Sam, could I come over tonight and shoot some lead balls into your pool?" :rotf:
I think they would cart me off to the ****y hatch! :rotf:
But I would give it a try if they were game, good idea! I do know of a guy I used to chat with that lived in California and did that very thing with black powder cartridge guns!
He'd shoot off the end of the diving board and get his grand kids to dive down and get his bullets as I remember it.

 

[M. De Land]

Clyde,as far as I know the molecular structure of pure lead does not change by compressing it once the load is removed.
What swaging does is remove all voids from casting providing for more uniformity in size,shape and weight.

 

[Col. Batguano]

Well, we have emperical evidence that id indeed DOES happen in that accuracy tends to fall off markedly below a certain powder level with one thickness patch, but takes a greater powder charge before fall off with a thinner patch.

Don't Ferguson and Lorenzoni rifles work on a similar principle? A smooth breech area and then a forcing cone of a sort to have the ball engage and swage to grab the rifling for the rest of the trip down the bore?

Measuring the before and after belted regions might work if you shoot in to a swimming pool, as the ball isn't going to gain any more rifling marks as a result of it's quick decelleration in the deep end, but you're right in that it MAY obdurate some more.

Like so may other things on this forum, when Pletch does the experiment, we'll all know for sure. He's a great resource here and we're lucky to have him.

 

[George]

Like so may other things on this forum, when Pletch does the experiment,. we'll all know for sure.

Yeah, I'll wait for Pletch's pictures. I've always thought there is no way to catch balls without causing more upset. If it occurs, it's because of all the energy applied at the back of the ball. When it is stopped, by whatever means, the same energy is applied to the front. Back or front, the deformation will be the same, a shortened and widened ball. I suspect the only uncontaminated way to see it will be with in-flight photos and careful measurements by someone with the right gear.

Spence

 

[M. De Land]

From what I could see and measure using a caliper and 2.5 power otivisor magnifier was that the patch weave imprint width trended to increase in spite of impact deformation which would tend to make it shorter, as the charge progressed up to 40 grains.
At 50 grains the expansion seemed to be no larger than the 40 grain charge.

 

[Black Jaque Janaviac]

No doubt. In-flight photographs should lay the question to rest. Kind of like photographing the Earth from the Moon. You can sail around the Earth and surmise that it is round. But then when you SEE that the Earth is round the debate is over.

 

[Col. Batguano]

But then when you SEE that the Earth is round the debate is over.

It's obturated too.
:stir:

 

[George]

It's complicated to imagine what the profile would be in the different situations. Pressure of the gas in the barrel would make a shorter ball with a wider equator belt, a sort of cylinder, I would think, but the ball couldn't be wider than the bore. Impact, on the other hand, would also make it shorter, but since the width isn't constrained by the barrel, it could be wider than the bore, but wouldn't have a wider belt. Adding deformation caused by impact to that formed on ignition would make for a complicated end result, and I don't know how you would separate the two.

Spence

 

[M. De Land]

I guess the point I'm trying to make Spence is that in acceleration from powder ignition or deceleration from impact I don't see a scenario/vehicle other than obturation where in the weave imprint would widen (front to back) as it did in the tests.

 

[coloradoclyde]

Clyde,as far as I know the molecular structure of pure lead does not change by compressing it once the load is removed.
What swaging does is remove all voids from casting providing for more uniformity in size,shape and weight.

I wonder about the Bauschinger Effect.
Since swaged lead ball are made from extruded lead wire that is then compressed.

 

[M. De Land]

I hope some one else will do something similar as well to lend a larger body of discovery to what I found.
Actually I'm considering running the whole thing again to see if the results can be repeated as I discovered several things in the doing of it that could be improved on that could firm up or disprove my initial findings.
1. A longer stove pipe tube so no paper is impacted.
2. A more uniform method of tamping down of the sawdust in the pipe for more consistent capture media compression.
I was very satisfied with the consistency of the ball seating using my brass pistol range rod with the large knob on the end.

 

[M. De Land]

Clyde, I can do a hardness test of a shot ball and one fresh from the box to see if there is any BHN change.
I believe the Bauschinger effect has to do with steel,brass and aluminum with a polycrystalline molecular make up. Lead has a cubic crystalline structure from what I read but this stuff is way above my pay grade.

 

[George]

I guess the point I'm trying to make Spence is that in acceleration from powder ignition or deceleration from impact I don't see a scenario/vehicle other than obturation where in the weave imprint would widen (front to back) as it did in the tests.

Yes, I understand your point, and it seems logical. Wouldn't the effect on the weave imprint of impact be to widen it side-to-side? Can you measure that?

Spence