Thoughts on "load inertia"

[Larry Pletcher]

Its the initial acceleration that causes the ball to deform, assuming it does very much. The pressure just causes the the acceleration which, if fast enough, moves the back faster than the front and causes the projectile to deform.

In digging balls out of back stops I can say that the marks put on the ball by the lands look no different than one started in the muzzle and then pulled back out. But its impossible to measure a ball shot into any surface that will cause it to deform on impact.
This is why the oiled sawdust thing would be great.
Now an undersized bullet such as a 500 gr 45 will show obvious signs of complete upset to fill the bore.
The patched bullet is a little harder to read.  I would love to see what e of the 40 caliber pickets looks like as it clear the muzzle but they do not survive back stops well at all.

Dan

Hi Dan,
I am looking into a method of studying this that involves a photo flash of amazingly short duration.  This flash has photographed a modern bullet at 2800 feet/second clearly enough to examine the rifling marks.  If such a tool could be used, we could simply photograph the ball/bullet as it leaves the barrel.  I can do this now with a ball at 1000 fps, but at real world speeds one needs something more. 

Regards,
Pletch

[hanshi]

Just as an observation I've detected patch weave marks on fired lead balls on occasion.  Since recovering a fired ball is a rarity, I can't say if this is an anomaly or not.

[Daryl]

Weave patterns on the ball will Always occur with a .005" under ball and a .025" patch.

[longcruise]

Weave patterns on the ball will Always occur with a .005" under ball and a .025" patch.

This is a .530 ball and .023 patch.



Weave is imprinted all the way around the ball to the mid point. 

I am looking into a method of studying this that involves a photo flash of amazingly short duration.  This flash has photographed a modern bullet at 2800 feet/second clearly enough to examine the rifling marks.  If such a tool could be used, we could simply photograph the ball/bullet as it leaves the barrel.  I can do this now with a ball at 1000 fps, but at real world speeds one needs something more.

Seems like there will need to be a way of determining if any change in shape happened during loading or shooting.  Maybe one could load a few balls and pop them out with the patch material at the muzzle or shoot them into a medium with five grains or less of powder?

Its the initial acceleration that causes the ball to deform, assuming it does very much. The pressure just causes the the acceleration which, if fast enough, moves the back faster than the front and causes the projectile to deform.

True, the ball can only accelerate in one direction.   However, the pressure all around the ball up to the equater is attempting to cause the ball to accellerate and therefore serving to nullify the deformation in any direction. 

I got absolutely no way of proving this theory.  It's just the way I think about it.

I do not believe your diagram is properly representative of the pressure acting on the ball.  The pressure, or force vector, would properly be depicted in context of its action perpendicular to the cross sectional area of the ball and parallel to the bore, vector oriented toward the muzzle. The way it is depicted in the diagram would lead one to believe there is force applied on the ball, perpendicular to the bore, or close to it.

That would be appropriate in the case of a flat based projectile, but the pressure can't help but surround the ball and apply pressure all around the under side half of the ball.  Ultimately the gasses (pressure) travel and are expelled parralell to the bore but That would not seem to change how the pressure is applied to the ball.

[Dphariss]

Hi Dan,
I am looking into a method of studying this that involves a photo flash of amazingly short duration.  This flash has photographed a modern bullet at 2800 feet/second clearly enough to examine the rifling marks.  If such a tool could be used, we could simply photograph the ball/bullet as it leaves the barrel.  I can do this now with a ball at 1000 fps, but at real world speeds one needs something more. 

Regards,
Pletch

Hi Larry
Once the smoke problem was defeated this is an excellent idea.
Might have to photo the ball a few feet from the muzzle.
I have been on both sides of the upset in RBs issue. I used to be on the no upset side, now I am not so sure, still would not put money on either theory. I really doubt the typical 54 rb is going to upset with FFG powder I think its too slow. FFFG might and I suspect this might be why some of the 54-58 cal guns shoot FFFG better.
But the upset may be just enough to make a slightly tighter bullet fit at the lands. Its certainly not something that is going to seal the bore.
I have tried to recover a piece of a 132 gr 40 caliber picket bullet since this really should upset. Flat base, more weight for bore size. But it shoots best with pretty heavy powder charges and the pure lead pickets are just lumps of mangled lead even at 100-120 yards. The one piece I did recover did not seem to have upset at all. But the damage was such that its impossible to really come down on  one side of this or the other.
Needs more experimentation or an oiled sawdust box or pictures.

Dan

[Larry Pletcher]

Hi Larry
Once the smoke problem was defeated this is an excellent idea.
Might have to photo the ball a few feet from the muzzle.
I have been on both sides of the upset in RBs issue. I used to be on the no upset side, now I am not so sure, still would not put money on either theory. I really doubt the typical 54 rb is going to upset with FFG powder I think its too slow. FFFG might and I suspect this might be why some of the 54-58 cal guns shoot FFFG better.
But the upset may be just enough to make a slightly tighter bullet fit at the lands. Its certainly not something that is going to seal the bore.. . .snipped . . .Needs more experimentation or an oiled sawdust box or pictures.

Dan

Hi Dan,
I'm sure you remember the questions I sent your way working on this patch separation project.  If velocity and flash limitations don't get in the way, the current topic could be a logical extention of the patch/ball separation work.
 
(.40 caliber ball app. 26-30" from muzzle about 1000 fps)


In the pic above I had the additional problem of trying to focus the camera at a shorter distance.  I have a camera now that will do much better.   If I were to repeat the photo above with my current camera I could pretty much fill the frame with patch and ball. 

Assume that we had a ball/patch  combination that left cloth marks on the lands but not in the grooves when we loaded it in the muzzle and pulled it back out by the cloth.   If we could get a photo that showed cloth marks in the grooves as the ball passed the camera,  we could logically say those cloth marks were caused by the bumping up of the ball when it was fired.

The biggest problem with this would be the short duration of the flash.  The photo above was fired at 1000 fps.  I'm sure that we would need to fire a ball at a much higher velocity to approach a speed where any bumping up would occur - if any did.  As the velocity increased, we would likely begin getting an elongated ball.  The flash system I described in an earlier post was one whose flash duration was measured in millionths of a second.    We don't need to stop an '06 at 2800 fps but we might need to get to 2000 fps to see any cloth marks made during firing - again - if there are any.  If I'm lucky I may get some contact info on such a flash.  Normal flashes don't come close.  The one I used for the pic above was "tampered with" a bit.

Regards,
Pletch

[Dan]

Quote
I do not believe your diagram is properly representative of the pressure acting on the ball.  The pressure, or force vector, would properly be depicted in context of its action perpendicular to the cross sectional area of the ball and parallel to the bore, vector oriented toward the muzzle. The way it is depicted in the diagram would lead one to believe there is force applied on the ball, perpendicular to the bore, or close to it.

That would be appropriate in the case of a flat based projectile, but the pressure can't help but surround the ball and apply pressure all around the under side half of the ball.  Ultimately the gasses (pressure) travel and are expelled parralell to the bore but That would not seem to change how the pressure is applied to the ball.

You are correct about applied pressure, I was confusing terminology in the previous. It is however, the force and resultant acceleration vs. resistance to same(Sectional density/inertia) which promotes obturation. 

Frankly I am quite certain that PRB do not obturate to the degree found in conicals, however, it is a long leap to imagine they do not obturate to some degree. Question is, how much?

[Daryl]

Dan- how much goes back to the load - finer (faster) powder as Dphar suggests vs. coarse (slower) powder.  Indegree, I agree it might happen, but not much more than a couple thou.  This is difficult to prove, of course. As suggested, what would be needed is a ball/patch combination that doesn't go to the bottom of the grooves - maybe .001" short of that and photgraph with a descent charge to see if the ball is marked by the bottom of the groove & if so, then go with .002" short of marking in the bottom of the groove, etc. to 'catch' the amound of obturation. BUT - that conclusion would only be valuable for that rifle barrel, ball and patch.  Antoher load, a bit looser or tighter, or different calibre might not obturate and if it did or not, would have to be retested.

[longcruise]

Frankly I am quite certain that PRB do not obturate to the degree found in conicals, however, it is a long leap to imagine they do not obturate to some degree. Question is, how much?

Like DanP, I've been on both sides of the question and still am not sure what to think.  Just throwing out food for thought.

Pletch might be on to something with his attempts to phota weave imprints in the grooves!

[Larry Pletcher]

Dan- how much goes back to the load - finer (faster) powder as Dphar suggests vs. coarse (slower) powder.  Indegree, I agree it might happen, but not much more than a couple thou.  This is difficult to prove, of course. As suggested, what would be needed is a ball/patch combination that doesn't go to the bottom of the grooves - maybe .001" short of that and photgraph with a descent charge to see if the ball is marked by the bottom of the groove & if so, then go with .002" short of marking in the bottom of the groove, etc. to 'catch' the amound of obturation. BUT - that conclusion would only be valuable for that rifle barrel, ball and patch.  Another load, a bit looser or tighter, or different calibre might not obturate and if it did or not, would have to be retested.

That is the problem.  There are huge combinations of variables.  One would only be able to say that with this particular set of variables this is what happened.   If this is approached looking for a clear cut answer that applies across the board, we'll not find it.   We might be able to say that obturation takes place within a very narrow environment of variables.  Or maybe not.   

Regards,
Pletch

[Daryl]

That is the problem.  There are huge combinations of variables.  One would only be able to say that with this particular set of variables this is what happened.   If this is approached looking for a clear cut answer that applies across the board, we'll not find it.   We might be able to say that obturation takes place within a very narrow environment of variables.  Or maybe not.   
Regards,
Pletch
[/quote]

Agree - completely.

[Larry Pletcher]

The possibility of measuring obturation with photos got me thinking about the methods.  I played around a little to see what kind of problems might have to be overcome.  The ability to get close enough and in focus can be solved.  The pics below should give us a close enough look to see cloth marks - if any are made.   On the first I left the ball unmarked.  In the sceond I rolled the ball over a rasp.  They both make me think cloth marks will be visible.


(Obviously these are taken of a motionless ball.)




The photo will be done by the ball breaking an infrared beam to trigger the flash. I have done that before.  Takes some set up time, a benched rifle, and a good man behind the gun.  I have all three.

The remaining issue is what happens when the ball is traveling at speed.  I can stop a ball traveling 1000fps, but have not tried faster.  I don't know the extent of the blur could be present.  Only time will tell.  Flash duration needs to be short.  Mine can be manipulated.  We'll see.

Regards,
Pletch

[Daryl]

Good luck on an interesting project, Larry.

[powderman]

Advanced notice.
This is an uninformed, out of the box idea.

Is there any way to test the patch material for the presence of lead at bore contact points?
i.e. does the lead ball impresses itself INTO the cloth with varying "density" and if so can it be made to "show up" in a CSI type test?

A solid ring of lead residue would imply a fattening of ball into grooves.
A dashed ring means lead was not pressed into grooves.

Maybe put some sort of micro-thin coating on the ball and test for that?

Just thinking out loud.

[Larry Pletcher]

Advanced notice.
This is an uninformed, out of the box idea.

Is there any way to test the patch material for the presence of lead at bore contact points?
i.e. does the lead ball impresses itself INTO the cloth with varying "density" and if so can it be made to "show up" in a CSI type test?

A solid ring of lead residue would imply a fattening of ball into grooves.
A dashed ring means lead was not pressed into grooves.

Maybe put some sort of micro-thin coating on the ball and test for that?

Just thinking out loud.

That is an idea that I had not thought of.  I'm not familiar with how a test for the presence of lead would work.  There may be folks in this group that know.  Maybe someone can fill in some gaps.  Thanks for thinking out loud.

Regards,
Pletch

[Daryl]

Advanced notice.
This is an uninformed, out of the box idea.

 
A solid ring of lead residue would imply a fattening of ball into grooves.
 
 Just thinking out loud.

I am sure that is what happens every time I load.  The lands and grooves impress into the ball, all the way around. I suspect is some sort of lead testing was done, it would show microscopic traces in a line around the patch/ball contact, heavier on the land areas, just as the impressions appear on the ball.

[powderman]

Maybe this problem can be submitted to MythBusters and have them do all the work! 

Actually, I am really looking forward to seeing some testing from the real experts here.

[powderman]

I just tried starting both .490 and .495 balls into each of my two fairly fresh Lyman GPR rifles. 
Pulled out the flush ball by tugging on uncut pillow ticking patch material.
There is no trace of impressed cloth pattern on any part of the ball except where the lands are.
i.e. the grooves did not press cloth pattern into the lead ball.

-----

Google returns a a site on lead residue testing in police work.
http://www.firearmsid.com/A_distanceExams.htm

The sensitive chemical is "sodium rhodizonate".
Maybe some commonly available home test kits have it. (for lead paint etc.)

I looked at all the labels on my breakfast cereal, toothpaste, potato chips, chicken soup, etc hoping to find a cheap source for this stuff but no luck so far.

[longcruise]

I always thought the gray ring on the ball side of the patch (bottom couple of rows) WAS lead...

I've thought it to be fouling wiped off the bore and into the patch while loading.

[Daryl]

I just tried starting both .490 and .495 balls into each of my two fairly fresh Lyman GPR rifles. 
Pulled out the flush ball by tugging on uncut pillow ticking patch material.
There is no trace of impressed cloth pattern on any part of the ball except where the lands are.
i.e. the grooves did not press cloth pattern into the lead ball.

-----

Google returns a a site on lead residue testing in police work.
http://www.firearmsid.com/A_distanceExams.htm

The sensitive chemical is "sodium rhodizonate".
Maybe some commonly available home test kits have it. (for lead paint etc.)

I looked at all the labels on my breakfast cereal, toothpaste, potato chips, chicken soup, etc hoping to find a cheap source for this stuff but no luck so far.

Powderman - had you used a tighter ball/patch combination, there would have been cloth marks from the grooves as well.

[Dan]

Larry, I would imagine you can get some traction with photographic analysis on this.  It is not my area of expertise by a long shot, but I note the boys working in the gubermint labs such as Aberdeen and use photos and mm wave length radar to ascertain painfully small measurements of pitch and yaw on conical bullets.  Good luck with it in any case....I shall of necessity stick with the medieval technology of oiled sawdust boxes.

[powderman]

Daryl - I doubt that many typical shooters use a ball that is more than 0.005 under bore size.
i.e. a .495 RB in a .500 (land to land) bore.
I'm not sure what the groove depth is for sure but "think" it's like 0.005-0.010.
Larger than .495 (for 50 cal) is not available in most stores.
The pillow ticking was typical as found in yardage stores.
i.e. about 0.015 thick.
I can forcefully compress it with my micrometer down to maybe 0.004
I'm not using a mallet to start the ball just a short starter and a hard slap.
I can't push the ball in with my fingers.

I think the gist of the question here is, shooting a normal PRB combination, is there any obturation or fattening of the ball when fired. And if so, how much. And what parts do lead purity, loading compression, powder charge/granulation and fouling play. What provides resistance at the moment of ignition to assist in obturation if any.

Also, when I pulled the ball there was no obvious evidence of lead on the patch material. I took a ball and rubbed it hard back an forth on the patch material and was then able to see some lead deposited. Some looked like flakes from a file.
Just abrading by cloth which wouldn't occur in the barrel.

I tend to agree with longcruise that the readily visible stuff on the patch is probably fouling residue and lube/spit absorbed into the cloth.

But who knows for sure until some bright guy here can figure out what's actually going on through testing with the right skill and equipment?
I'm looking forward to it as much as I appreciated the high speed video/data of flintlock ignition. Incredible.

[powderman]

This is interesting.
I just found another thread, on a different Forum where several people said:

*They could not find any cloth impression marks in the GROOVE area of the ball.
*They could not find any cloth impression marks in the LAND area of the ball.
  (Maybe see a little with a magnifying glass)
*No obturation occurs in PRB since they didn't see any cloth patch weave marks even on fired balls recovered from various sources.

I thought maybe they were talking about the backside of the ball.
I don't think so since one guy was talking about shooting marbles with great accuracy.

When one guy mentioned that he pulled balls and saw weave marks, someone said that it was the screw-type ball puller had expanded the ball and forced it into the rifling.

http://www.muzzleloadingforum.com/fusionbb/showtopic.php?tid/223136/post/593197/hl/obturation/fromsearch/1/#593197

Go figure.

If testing is done make sure you document the condition of unfired, pulled balls.

Post modified as per forum rules.
Daryl

[Dphariss]

This is interesting.
I just found another thread, on a different Forum where several people said:

*They could not find any cloth impression marks in the GROOVE area of the ball.
*They could not find any cloth impression marks in the LAND area of the ball.
  (Maybe see a little with a magnifying glass)
*No obturation occurs in PRB since they didn't see any cloth patch weave marks even on fired balls recovered from various sources.

Oh brother....

I strongly suggest that before you believe this "information"  that you do your own research.
Bigger balls show more cloth imprint than smaller balls will.
Unless very loose fits are used all will show marks where the lands impress the patch into the ball.
One other thing seldom have I had to screw a puller very deep in the ball to pull it.
But then I know how....
In a 54 ball you need to turn it in past the 1/2 way point to swell it at the point where the lands bear on the ball.

Dan

[Larry Pletcher]

I think you all realize that there isn't going to be a quick, easily found answer to this.  There are many issues to solve other than the ability to get a decent photo.  But, that's where I'm likely to start - if I can't get a photo that shows cloth marks on the lands, I certainly won't be able to photograph cloth  marks in the grooves. 

We will likely use a .58 belonging to Steve Chapman, who will be the man behind the gun.  (He has to fire the shot, stacking one ball on top of another in a completely dark room. BTW, that's the least of my worries.)   I want a ball/patch load that shows cloth marks on the lands at 1000 fps in clear focus.  That will be the control for our basis of comparison - both for flash issues and for the amount of cloth marks.  If we are successful with this, then we can continue.

In going beyond, lands and groove depth and width must play a huge part of this.  The best I know is to adapt as we begin to get information.

This is going to be on the back burner for a short time at least.  We're doing some last minute work this week getting ready to do our flint vs percussion vs mule ear timing.   Steve and I don't think this will be a long drawn out process, but who knows.   (This project was conceived in Jim Chambers booth at Friendship.  His pistol kit stock and small Siler locks will be the basics for this along with a custom mule ear made on a s Siler plate.)

Regards,
Pletch