How do I determine muzzle velocity w/o a pendulum?

[CaniblCat]

Hi all,
I don't use black power guns, but my friend Teleoceras does and he suggested I post my question here. So here goes:

I am doing a paper for my physics class on firearms and I need to know if anyone has a formula to determine muzzle velocity that doesn't involve a pendulum or the use of gravity.

Is there a way to determine velocity using only the mass (grains) of the bullet and the statistics of the gun (like the barrel length). ?

For example, I have a .22 long rifle that remington states is 40 grains and has a muzzle velocity of 1150 fps. How do they determine that velocity? Can you do it without a pendulum?

Thanks in advance for anyone that can help.

 

[Stumpkiller]

What is done is to fire it over two light sensitive detectors that are a set distance apart. The time it takes the shadow to travel between them is used to determine velocity. They are called Chronographs and are relatively inexpensive.

The poor man's test is to listen for when the rifle first "cracks" which means the projectile has exceeded the sound barrier (right around 1,000 fps).

 

[loophole]

Muzzle velocity is a function of the energy produced by the powder charge, the weight of the projectile, barrel length and some internal ballistics factors which have only a very minor effect. If you understand the chemistry of black powder and the physics involved in converting that energy to accelerating the ball, (which I don't) you can compute the energy produced by a charge of a given weight of powder, then compute the duration of acceleration, and derive a theoritical muzzle velocity. Nobody I know does this--if we don't have a chronograph (early chronographs were pendulums) we use data published in loading manuals.

 

[Stumpkiller]

Are you doing this as a project? I can tell you an elegant little emphirical method of calculating velocity with simple measurements and equipment, but it is a tad involved. A physics teacher would love it, but also come up with several reasons why it wouldn't work (but you'd know better because you got it here :winking.

As far as a formula, you would need to know the energy of the powder and the friction of the barrel. Unfortunately, the old method of determining the energy of the powder was with a pendulum, so you're back to square one.

Pressure was also determined by how much a piece of copper wire was crushed when placed in the chamber wall, and now it is a piezo-electric stress gauge that measures it.

Somewhere I have a constant figure for velocity based on weight of projectile to weight of black powder, but .22 cartridges don't use black powder.

 

[CaniblCat]

and somehow I doubt the university will approve of me brining my ruger to school and firing off a round to get the velocity.

 

[crockett]

Theoretically, you should be able to determine velocity by simply plugging all the variables into a formula, the powder charge,compression, bullet weight, bullet ogive, barrel length and caliber, depth of rifling, lead bullet versus copper jacket, etc. The variables are endless. The problem is that modern equipment measures the actual speed of the projectile so your approach is impractical and in our world impractical approaches aren't followed up on even though maybe they should be just from the point of interest. Those who reload modern ammunition try for consistent loads but even then the speed varies.
The pendulum and gravity I believe were the traditional tests and by today's standard not that great. I've actually used bullet drop between distances as a very crude method of what is happening- velocity wise- at longer distances. The dual screens are typically used a few feet off the shooting bench and measure intial speed.
There is a book out called Ballistics. It costs about $25.00 and has all the "Rocket Science". Barnes and Noble stocks it and most gun catalogs carry it.
Modern bench rest shooters are cream of the crop on the accuracy game, trying for one hole groups at long ranges. If there is a group in your area you could talk to them.

 

[Stumpkiller]

Bah! That's the problem with today's youth. Ya can't learn 'em the proper stuff 'cause of all the social baggage we drag around.

Heck, half my shop class in high school were making zip guns when the teacher was busy drinkin under his desk. Where else you gonna learn good stuff like that?

That's why we've never been back to the moon. Young minds are too stifled today.

You tell your teacher physics was developed to explain firearms, not the other way around. :crackup:

 

[Teleoceras]

Hi all,
I don't use black power guns, but my friend Teleoceras does and he suggested I post my question here.

Oh, you will be shooting some of my girls once the weather gets more agreeable. Damn rain! :curse:

Next time at the range, you will know WHY I am so passionate about the black powder guns. :results: ::

 

[TANSTAAFL]

Try this, he is a pretty sharp guy.

http://www.ctmuzzleloaders.com/mlexperiments/rbballistics/rbballistics.html

 

[CaniblCat]

Thanks everyone for all the help. You guys are awesome!
Unfortunately, the book won't be of help as our :curse: professor requires all our sources to be from web pages! :curse: :curse: :curse:

Ah, well, I suppose I could always say "The manufacturer (in this case, Remington) provides the muzzle velocity of the bullet, which in this case is actually true.

Thanks again!

 

[musketman]

You forgot to figure in drag from the barrel, air resistance, standard day temperature and the planet Jupiter... <OMG> :winking: :haha:

Barrel length will play a big roll in velocity, the longer burn time of the powder, the more push it will have and the faster it will go...

Example:
.36 caliber muzzleloader using a 71 grain .360 patched round ball loaded with 25 grains of FFFg black powder...

Everything is the same except barrel length:

28" barrel gives 1329 fps velocity...
32" barrel gives 1335 fps velocity...
37" barrel gives 1384 fps velocity...
43" barrel gives 1521 fps velocity...

So the barrel length is a major factor in velocity...

In the same barrel lengh (let's use the 32 inch one) all things the same except charges...

25 grains of FFFg in a 32" barrel gives 1335 fps velocity...
30 grains of FFFg in a 32" barrel gives 1457 fps velocity...
35 grains of FFFg in a 32" barrel gives 1579 fps velocity...

This calulates to 24.4 fps increase per grain of powder...

1579 fps - 1457 fps = 122 fps / 5 grains (difference between two loads) = 24.4 fps per grain loaded in that barrel...

 

[Keith]

Thanks everyone for all the help. You guys are awesome!
Unfortunately, the book won't be of help as our :curse: professor requires all our sources to be from web pages! :curse: :curse: :curse:

Ah, well, I suppose I could always say "The manufacturer (in this case, Remington) provides the muzzle velocity of the bullet, which in this case is actually true.

Thanks again!

That source requirement is strange. There is some great information on the web. This site for instance. However some of it is absolute manure. There is a site wikipedia (sp), that is an online encyclopedia, that allows users to edit the material. How good a resource is that?

Any way one thing I would suggest is looking at the Mad Monk's page Teleo has a link off his webpage I believe.

 

[robinghewitt]

and somehow I doubt the university will approve of me brining my ruger to school and firing off a round to get the velocity.

Then you can't do it, all you can do is look up the measured data on an earlier shot.

OTOH, if you can't shoot the gun I don't see why you aren't allowed to use gravity and pendulums????

 

Squire
Maybe Elmer Fud will give up his cork gun to do a baliatic test with if you can get him from hunting them rascaly lil wabbits. :crackup:

OH maybe not it don't use BP :blah:

Woody

 

[Stumpkiller]

Unfortunately, the book won't be of help as our professor requires all our sources to be from web pages!

Well that's the opposite of what I would have expected. I guess the prof/school has accepted the inevitable and wants to know where we really get our information.

Remington has ballistic tables on their website. You can get the standardized info there

 

[Teleoceras]

Stumpkiller:

Unfortunately, the book won't be of help as our professor requires all our sources to be from web pages!

Well that's the opposite of what I would have expected. I guess the prof/school has accepted the inevitable and wants to know where we really get our information.

Remington has ballistic tables on their website. You can get the standardized info there

I know Cat in real life. He is a computer programming major in college. This project is part of one of his web classes.

His recent rekindling interest in firearms is what prompted his topic choice in his assignment.

Cat is interested in trying some of my muzzleloaders this year. Hopefully that will spark a great interest in the old arms. :hmm:

 

[TANSTAAFL]

Might as well refere him over here to the Handgonne page so he can be-gonne down the same track as you.
:crackup: :crackup:

http://www.musketeer.ch/blackpowder/powder_frameset.html