Smoothbore ball velocity

[George]

Wandering yes, slowing more, no.

I agree with that, except the wandering part. Can't think of any reason spin would preserve velocity.

Spence

 

[duelist1954]

Here are the results from the video test I did on smoothbore round balls


https://imgur.com/VwG0Bam


https://imgur.com/9lTX1kc




Here’s the video

 

[Pukka Bundook]

Duelist,
Very good! Very thorough tests. Two thumbs up.
Right on about velocity being the important part, and 2 F reducing pressure. Good of you to share it with us. Thanks!


Spence,
I was meaning that a ball not spinning diverges from its path much quicker than one that Is spinning. (Poor word when I said "wandering"!

best,
R.

 

[George]

Well, diverge and wander are sort of the same, wander is to diverge and then diverge back. I understood you to mean that. It was what I was disagreeing with. I'm not convinced roundballs fired from smoothbores turn left at 50 yards as the dogma would have it.

Spence

 

[Pukka Bundook]

Hi Spence,

Yes, I too don't think a ball from a smoothbore turns left at 50! LOL.

 

[Herman Karl]

Using a chronograph I gathered muzzle velocities (15 feet from the muzzle) for a range of muzzleloaders. These data are representative and not definitive. Check out more velocity data in Lyman Black Powder Handbook (Ramage, ed.) 1975 and the works by Sam Fadala.


.75 caliber Brown Bess, 0.715”550 gr. ball, 0.010” patch, 80 gr. FFFG 825 fps

828 fps


.75 caliber Brown Bess, 0.715” 550 gr. ball, 0.015” patch, 80 gr. FFG 910 fps
100 gr. FFG 938 fps


.75 caliber Brown Bess, 0.690” 495 gr. ball, no patch, 80 gr. FFFG 666 fps


.75 caliber Brown Bess, 0.690” 495 gr. ball, 0.010 patch, 80 gr. FFFG 791 fps
734 fps


.77 caliber Brown Bess, 0.735 598 gr. ball, no patch, 120 gr. FFG 977 fps
702 fps


.68 caliber fowler, 0.662” 437 gr. ball, 0.010” patch, 60 gr. FFG 874 fps
929 fps
830 fps
60 gr. FFFG 1001 fps
1038 fps
1044 fps


.62 caliber fowler, 0.595” 317 gr. ball, 0.010” patch, 60 gr. FFG 927 fps
80 gr. FFG 1095 fps
100 gr. FFG 1242 fps



.45 caliber rifle, 0.440 128 gr. ball, 0.010”patch, 70 gr. FFFG 1500 fps


.32 caliber rifle, 0.311 45 gr. ball, 0.010” patch, 30 gr. FFFG 2000 fps


For a discussion of the two tables below read the my paper, “Comparison of strength of 18thcentury and contemporary black powder: eprouvette data.” The link to the reference is provided below.

Table in Roberts, N.A., Brown, J.W., Hammett, B., and Kingston, P.D.F. (2008) A detailed study of the effectiveness and capabilities of 18thcentury musketry on the battlefield. Journal of Conflict Archaeology 4:1-21

My notations are in the margins.

Table in Robins, B. (1805) New principles of gunnery … . a new edition by Charles Hutton, Reprints from the collection of the University of Michigan Library

My notations 1690 and 1173 are the velocities in fps converted from Robins data in the table.

For more information based data I recommend reading the following:

Live fire discipline of a minute company

https://www.scribd.com/document/333334509/Live-Fire-Discipline-of-a-Minuteman-Company

Comparison of strength of 18thcentury and contemporary black powder

https://www.scribd.com/document/394...of-18th-Century-and-Contemporary-Black-Powder


Muzzleloader blank powder charge pressure: Are double charges dangerous?

https://www.scribd.com/document/394...-charge-pressure-Are-double-charges-dangerous

 

[Grumpa]

In the posting I was referring to (off another blackpowder forum that I don't normally visit) the claim was that the spin imparted to the ball shot from a rifle accounted for it retaining speed better than the ball shot from a smoothbore. I don't know if that is true or not, I was adding grist to the mill for the OP's question.

No one is questioning that the balls and guns under discussion have enough "whompability" to take down any animal on this continent. The OP wanted to know if a ball shot from a smoothbore will be slower than one from a rifle, both propelled by black powder (which works differently than smokeless powder). This is a hypothetical question ; comparing rifle "A" to smoothbore "B" requires an elimination or at least a minimization of all variables - bore size, ball diameter and weight, patching thickness, lube, wadding material etc. etc. etc. (Two identical modern firearms from the same maker can record different velocities from identical ammunition - and that's fired at the same time/location. Imagine the difficulty of a true comparison between different types of muzzleloaders.)

OP stated that he did chronograph the load once and got an average velocity of 1488 fps! THAT puts the lie to those who argued with him and claimed "750".

The question raised is an interesting one. Hopefully, someone on the Forum has enough understanding of the Physics involved to give us a "scientific" answer.

Richard/Grumpa

 

[Herman Karl]

In the posting I was referring to (off another blackpowder forum that I don't normally visit) the claim was that the spin imparted to the ball shot from a rifle accounted for it retaining speed better than the ball shot from a smoothbore. I don't know if that is true or not, I was adding grist to the mill for the OP's question.

No one is questioning that the balls and guns under discussion have enough "whompability" to take down any animal on this continent. The OP wanted to know if a ball shot from a smoothbore will be slower than one from a rifle, both propelled by black powder (which works differently than smokeless powder). This is a hypothetical question ; comparing rifle "A" to smoothbore "B" requires an elimination or at least a minimization of all variables - bore size, ball diameter and weight, patching thickness, lube, wadding material etc. etc. etc. (Two identical modern firearms from the same maker can record different velocities from identical ammunition - and that's fired at the same time/location. Imagine the difficulty of a true comparison between different types of muzzleloaders.)

OP stated that he did chronograph the load once and got an average velocity of 1488 fps! THAT puts the lie to those who argued with him and claimed "750".

The question raised is an interesting one. Hopefully, someone on the Forum has enough understanding of the Physics involved to give us a "scientific" answer.

Richard/Grumpa

You hit the nail on your head both with you "two identical modern firearms" and especially with the last sentence that applies to so many comments on these web forums. I won't comment on the spin effect of rifling it would be a waste of time.

 

[Herman Karl]

In the posting I was referring to (off another blackpowder forum that I don't normally visit) the claim was that the spin imparted to the ball shot from a rifle accounted for it retaining speed better than the ball shot from a smoothbore. I don't know if that is true or not, I was adding grist to the mill for the OP's question.

No one is questioning that the balls and guns under discussion have enough "whompability" to take down any animal on this continent. The OP wanted to know if a ball shot from a smoothbore will be slower than one from a rifle, both propelled by black powder (which works differently than smokeless powder). This is a hypothetical question ; comparing rifle "A" to smoothbore "B" requires an elimination or at least a minimization of all variables - bore size, ball diameter and weight, patching thickness, lube, wadding material etc. etc. etc. (Two identical modern firearms from the same maker can record different velocities from identical ammunition - and that's fired at the same time/location. Imagine the difficulty of a true comparison between different types of muzzleloaders.)

OP stated that he did chronograph the load once and got an average velocity of 1488 fps! THAT puts the lie to those who argued with him and claimed "750".

The question raised is an interesting one. Hopefully, someone on the Forum has enough understanding of the Physics involved to give us a "scientific" answer.

Richard/Grumpa

Re: understanding of physics. It's bemusing how often "authorities" cite Newton's Laws of Motion (usually only "for every action there is an equal and opposite reaction as it's likely the only one they have heard of). The trouble is they almost always apply the laws incorrectly.

 

[Grumpa]

I went to the Physics Forum, section on Mechanical engineering ...I am quoting Michael D. Sewell ( who is a long range M1 Garand shooter) : "The spin of a rifle bullet is for stability in flight only, which is in turn for accuracy....you have to pay for the spin with velocity....Spinning increases the total aerodynamic drag." (Please note that I am quoting answers NOT to my specific questioning, but taken from a discussion on "Spinning Bullet, Why?") Also, theoretically, some of the force that would be used to propel the ball is used to force the ball into and through the rifling.

So...what I am reading would suggest that the rifle would have LESS velocity than the smoothbore, all other things being equal.

C'mon, I know we have engineers galore on this Forum, and lots of others with more understanding of these matters than I have...let's hear from you all. (Granted, this doesn't have a whole lot to do with Traditional Muzzleloading...or does it? I have seen quite a few historic articles presented by Spense, Artificer and others dealing with period efforts to settle questions like this.)

Richard/Grumpa

 

[Herman Karl]

Calculating drag is complex. My first question is how does Sewell know that spin decreases velocity? How much does it decrease velocity -- 1%, 0.1%, 10%, etc.? What factual information can he cite. I'm not questioning that it might be the case. I do want to see documentation.

My view is that an expert in fluid dynamics and projectile motion is needed to answer this question. I'm a retired scientist and have dabbled in fluid dynamics of sediment transport, but I don't have the physics background to answer the spin/velocity question. It wasn't relevant to my research. I skimmed a few documents on the Internet that I list below. It's complicated and in my quick review (I did not take the time to read these reports in detail) I did not find a quick answer that spin decreases velocity. More digging into the authoritative literature is necessary. It'a an interesting academic question, but of what practical value? Perhaps it would have value for long range artillery? I don't know.

https://www.emeraldinsight.com/doi/abs/10.1108/02644409510799758?journalCode=ec
An excerpt from the abstract of the paper above:
"The computed results show that, in comparison with the non‐spinning case, to increase the spin rate can result in increases in viscous drag and nose pressure drag, but can cause decreases in boattail drag and base drag. The variations of these drag components result in only a small (less than 5%) increase in total drag; thus the performance of the transonic projectiles is found to be insensitive to the spin rate."

Note these results are for transonic velocity and not supersonic or subsonic. It does not state that the velocity is decreased.

http://www.accurateshooter.com/ballistics/transonic-effects-on-bullet-stability-bc/

https://mysite.du.edu/~jcalvert/phys/ballist.htm

https://physics.stackexchange.com/q...cient-for-a-rotating-cyclinder-in-still-fluid

https://apps.dtic.mil/dtic/tr/fulltext/u2/a030430.pdf

As I said it's complicated!!

 

[Grumpa]

(Boy do I miss the old smilies!)

Thank you, Herman. I am going to bed. In the next day or so I will try to find time to approach these sites. I am thinking that this is far more obtuse than "which priming powder gives the quickest ignition in a flintlock?" and even less relevant to the real world of muzzleloading.

I am sincere in my thanks. This Forum is nothing if not fun. I'm always learning something new.

Richard/Grumpa

 

[Skychief]

Thanks Grumpa for post #27.

Best regards, Skychief.

 

[Ranger Boyd]

Independent of the spin vs. velocity question, don't forget that the tighter seal created by the patched rifle ball engaging the rifling creates less windage losses and higher overall pressures at ignition. The smoothbore comparisons above show 50-100 fps differences between like loads patched vs. unpatched and demonstrate the principle. The tighter fitting rifle ball would likely show even less loss of velocity due to windage and higher breech pressures (hence more velocity imparted over the length of the barrel). Bore friction would of course be increased somewhat in a rifle, but I have a hunch it is a minor factor by comparison.

It is, of course, as many have pointed out, an empirical question...

In any case, I tend to believe that the initial muzzle velocity difference is the decisive factor, vice any additional parasitic drag losses.

 

[George]

For more information based data I recommend reading the following:

A couple of useful links re the works of Benjamin Robins:

https://play.google.com/books/reade...sec=frontcover&output=reader&hl=en&pg=GBS.PR1

http://arc.id.au/RobinsOnBallistics.html

Spence

 

[George]

In the posting I was referring to (off another blackpowder forum that I don't normally visit) the claim was that the spin imparted to the ball shot from a rifle accounted for it retaining speed better than the ball shot from a smoothbore.

It seems to me there are two questions here, and that they are being conflated but need to be kept separate.

#1 Will the same charge of powder, ball size, barrel length, etc., in smoothbore and rifle result in the same muzzle velocity?

#2 Give the same muzzle velocities of identical balls, will a non-spinning ball from a smoothbore and a spinning ball from a rifle lose their velocity at the same rate?

These are two very different questions. I thought we were discussing question #2, the effect of spin.

Spence

 

[Ranger Boyd]

It seems to me there are two questions here, and that they are being conflated but need to be kept separate.

#1 Will the same charge of powder, ball size, barrel length, etc., in smoothbore and rifle result in the same muzzle velocity?

#2 Give the same muzzle velocities of identical balls, will a non-spinning ball from a smoothbore and a spinning ball from a rifle lose their velocity at the same rate?

These are two very different questions. I thought we were discussing question #2, the effect of spin.

Spence

Concur. My apologies, I thought both questions were still in play. Guess I haven't kept up. In any case, my point was that while both are interesting, question #1 has a more significant practical impact on the terminal ballistics.

 

[George]

Ranger Boyd, my comment was not directed at you, but at the board at large. Even this new marvelous software hasn't solved the problems which come from just getting at the end of the line to post.

Spence

 

[Ranger Boyd]

No worries. I should have been more clear.

 

[Rat]

Well, diverge and wander are sort of the same, wander is to diverge and then diverge back. I understood you to mean that. It was what I was disagreeing with. I'm not convinced roundballs fired from smoothbores turn left at 50 yards as the dogma would have it.

Spence

I observed an interesting, to me, thing when I was into paint ball. As you know, paint ball guns are smoothbores, and shoot a round projectile. I have a long barrel on mine. (yeah, still have it) I was shooting it off a porch, on a house built on the side of a hill, so you could shoot them out into space, and really observer the flight. The paint balls would fly very straight for a distance, (around fifty yards?) and then very distinctly make sharp turns to the right of left, or up or down. Maybe not up. Since seeing that, I believe that lead ball out of smooth bore does much the same, probably not to that extent. ??? Just an observation. It would certainly explain 3" groups at 50 yards, and 3-foot groups at 100. ?? Sorry if this has been discussed profusely before. And sorry to be off topic.