velocity


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dreamer1
May 17, 2006, 04:02 PM
First of what velocity should a lead bullet that is 13 mm in diameter and weights about 15 grams have to have good penetration and stopping power?
According to my calculations 350 m/s should be enough.
Could a black powder handgun accomplish this?

And how can I measure the speed of the bullet when it has just left the muzzle? Is there any cheap and easy way to do this?
Is there any alternative way to measure the stopping power? I read somewhere that if you fire a shot against a hard object like a metal plate and the bullet gets completely or largely deformed it means that the stopping power is good enough.

How do I determine the accuracy of my weapon? I understand that I should measure the distance to the target first and fire several shots at the same point and then measure again the distance from the centre of the target to the outer edge of the bullet that hit longest from the centre. And what should I do next to get figure of the accuracy?
Thanks.

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Jim Watson
May 17, 2006, 05:35 PM
I could not find specific data but 350 m/s (1150 fps) is probably more than the typical muzzleloading pistol velocity. You MIGHT could reach it with a large powder charge and a tightly patched ball.

Velocity measurement is commonly done with a counter chronograph, available in the US for less than $100. It can be done more cheaply but with considerable labor and calculation by means of a ballistic pendulum. The mathematics are shown here
http://www.musketeer.ch/blackpowder/handgonne.html
but the actual construction is not clear. I have seen good pictures of one made by suspending a log with two wires in line with the shot so that its swing will be more uniform.

There are many methods of evaluating "stopping power" to the level of whole books.

I will just comment that the US Army pistol from 1819 until the adoption of the revolver was a .52 calibre (13mm) percussion smoothbore loaded with a round ball and 35 grains (2.3 grams) of black powder and it was considered adequate to the task. The US Navy had a .54 calibre pistol which Henry Deringer furnished with a rifled barrel, although the original Ames built guns were smoothbores.

dreamer1
May 17, 2006, 07:32 PM
Hi

Thanks for the tips. The homepage was quite intriguing I have always been interested in the earliest forms of firearms. I am tempted to make one of that myself as the next project.

Actually I have already tested the experiment you linked to for acquiring the bullet speed. It was in physics class back in high school, I have forgotten the physics behind the experiment but I do remember that the results were pretty accurate. The thing is that the experiment canít be done by one person alone, several people need to be involved and take measurements and one firing the gun, we used a relatively harmless airgun btw.
I think it could be worth buying the chronograph, I donít live in the US but I guess it could be bough in my country as well, itís not that exotic.

How should I measure the accuracy?
Thanks again.

Bullet
May 17, 2006, 08:02 PM
dreamer1
I believe most people measure accuracy by group size. To do this simply shoot at a known distance 15 yards or 25 yards etc. Shoot 5 shots at your target then measure the distance between the two shots (holes) that are farthest apart, (outside to outside of the holes) then subtract the diameter of the bullet you are using. This number will be your group size at whatever distance your shooting.

Some people measure from the center of the two holes that are farthest apart, (without subtracting the bullet diameter) which will figure out to be the same as the other method.

By the way where do you live?

Art Eatman
May 17, 2006, 10:21 PM
"Ballistic Pendulum" is the Physics experiment. Measure the distance moved by the targeted pendulum. The length of the suspending string/wire/cable is known, as is the weight of the pendulum and the projectile.

But I disremember the method of actual calculation. :)

Art

Jim Watson
May 18, 2006, 12:15 AM
The Shooting Chrony is the least expensive electronic counter chronograph, models starting at US $90. It is available through distributors worldwide as shown on this page of their site:
http://www.shootingchrony.com/order_DOUT.htm

griz
May 18, 2006, 07:54 AM
13 mm is pretty big. That would be a 231.5 grain bullet in our units, so it would not take too much velocity to be quite powerful. For a comparison, the 45 ACP is considered a serious self defence caliber, and fires a 230 grain bullet at about 850 FPS.

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