Rifle vs. smoothbore/velocity/a test in planning

[Leonredbeard]

Gents,
a while back there was an arguement raging about which barrel would produce the more velocity. I weighed in saying rifling equals resistance equals confinement equals more efficient burn equals higher velocity. Well, I was basically patted on the head and the boys went back to the idea that less resistance meant higher velocity. This set me to thinking. So I have a friend who promised me the use of a chronograph in August.
Now I have a .62 smoothbore and a rifled .60 both pan and vent fired. I use the same ball and patch combo for both. I have to hammer the ball/patch into the rifled barrel and can thumb start the load in the smoothie. So this should be a good test. If resistance slows the load it should really slow it in this barrel. So the ball weight and patch weight will be identical in the average. This will not be an exhaustive test but should shed some experiential light on the question. Because bore relief will definately affect velocity, bigger/slower, smaller/faster, I plan to hammer a bare .59 ball down the bore of my .54 rifled. That way we have the same weight ball in the very smaller bore, and will give us an idea of how much bore relief affects velocity. I don't care how much the ball is deformed, I am not shooting for accuracy but for velocity. At fifteen feet the deformed ball will not lose enough velocity to affect the outcome of the test. Of course, I will use the same 80 gr. load of ffg in all three bores.

Understand, there is not as much resistance from rifling as one could be led to suspect. Lead is a dead metal having no springiness. Once formed to the rifling it is not all that tight. The one in sixty six twist will not hold the ball that much either. Therefore I will not make prediction as to the higher velocity. I am quite excited to do the test!

I think the test could be done with a rifled .62 and a smooth .62, but use a bigger ball. The problem with this comparison is that you cannot get the same bore relief from a smoothbore and a rifled gonne. Either the bore will be the same and the grooves will be bigger, increasing the bore relief. Or the bore of the smoothie will be the same as the depth of the grooves, as with my test and the bore relief will be decrease slightly in the rifled barrel. I suspect that the bore relief will have a large influence on the velocity.

God bless.
volatpluvia

 

[musketman]

It sounds very interesting, keep us posted...

 

[Herb]

I don't understand your test procedure, but will look forward to your results. I have done a lot of chronographing, and the results are not always what you would think. That is, a tighter patch with the same ball means more resistance, therefore you would think higher pressure and velocity. BUT: a looser patch or smaller ball give higher velocity. Have not tested any smoothbores.

 

[squirejohn]

A similar test was recently conducted. Check out the American Longrifles message board.

 

[thomas]

Actually, this test was first done in the 1740's. An Englishman named Benjamin Robins (also the inventor of the balistic pendulum) conducted a series of experiments and wrote a paper titled "Observations of the Natural and Advantage of Rifled Barrel Pieces", which he read before the Royal Society in 1747. He concluded that the smooth bore had higher velocity and deeper penetration than the rifled piece. Both smooth bore and rifled were equal in bore diameter and ball diameter and used exactly the same powder charge in each.

The guy was a very smart guy and very ahead of his time. He made a prediction that "whatever country shall thoroughly comprehend the nature and advantages of rifled barrel pieces and having facilitated their construction, shall introduce into their armies their general use with a dexterity in the management of them".

Thomas

 

[Leonredbeard]

Squirejohn,
I read the post with interest at Amlongrifles. I suppose the more of us conduct the test the more trust we can have in the eventual evidence we accumulate. So we shall see, hee hee!
God bless.
volatpluvia

 

[Stumpkiller]

I plan to hammer a bare .59 ball down the bore of my .54 rifled.

Two thoughts come instantly to mind:

1.) Not the best time to forget the powder.

2.) Could be rough on the tang inlet at the wrist. I've seen rifles with hairline splits there and I assume it was from either being dropped or the barrel pounded backwards as you intend.

But, it is a noble undertaking and I applaud you. :applause: An emperical test can remove most doubt.

But will a swaged bare ball settle the arguement for patched ball shooters in the "real" world?

Next question: Why? I don't use rifling because of speed. I use it because of accuracy. That's easy to measure with those 4" & 6" round dots on sheets of paper at 50 yards. :haha:

 

[thomas]

Stumpkiller,

Yep, you're right. That is exactly what Benjamin Robins was trying to say in his paper that he read (published in 1747).

All of the tests and experiments that he did were basically to prove and to make the public understand the superiority of a rifled firearm. His tests that proved a smooth bore was faster at the muzzle than a rifled firearm (everything being equal or the same)was just a minor thing in his paper.

He certainly wasn't trying to say the smooth bore was better. Most of his experiments had to do with what was the right rifling twist and he pretty much got it right, even back then. He even had the Forsythe principle (I'm not sure if I spelled that right or even if the name is right)down pat - slow twist, shallow rifling, large powder charges.

Thomas

 

[thomas]

The guys at American longrifles also said the vents weren't the same size [the rifle's was smaller]. That was the reason the rifle had alittle higher velocity. If both vents had been the same the rifle would have had the lower velocity.

When you do your tests & experiments make sure all is the same, otherwise nothing is proved at all.

Thomas