At what distance does a handgun round hit max velocity?

[Forseti]

Does anyone know at what rough distance a handgun round hits peak velocity?

I'm sure its dependent on barrel length, bullet weight, caliber, etc,...but I was wondering if there was a rough distance from about a 4" barrel...

It can't be that velocity tapers off after clearing the barrel...can it? Doesn't it continue to accellerate for a little bit more?

[WESHOOT2]

It starts slowing after it leaves the muzzle; air resistance, you know.

[Marko Kloos]

The highest velocity is reached at the muzzle. After the projectile exits the muzzle, the forces of gravity and friction will slow it down until its initial inertia is overcome.

[Pappy John]

Yep, its all downhill from the muzzle.

[Pistolsmith]

The only place I've ever seen a figure on this is in a very early Savage Arms catalog of the Lewis gun. It was claimed that gases thrusting from the muzzle and radiator accellerated a bullet some 30 to 35 feet a second. This was with the .30-06 cartridge. No distance from the muzzle was mentioned.
Since the chronographs we can obtain do not measure muzzle velocity, but instrumental velocity, we can't measure velocity until the bullet is in free flight several feet ahead of the muzzle. When the screens are placed closer, they register the speed of sound, due to the report. By the first screen, obviously, the bullet's velocity is in decline. Since it is impossible to measure velocity at the muzzle, it could be that when it frees itself from the friction of the rifling, it speeds up a slight amount. A smoothbore muzzle loader, firing an unpatched bullet, would, conversely, begin to slow at the muzzle.
Despite the fact that modern powders are progressive buring, a cartridge will attain maximum pressure at the precise instant that the bullet begins to move forward.
If you fire a bullet through an extremely long barrel, the bullet's velocity will begin to decline before the bullet leaves the muzzle. You can find the exact figures in some computer programs for internal ballistics.
A round unpatched ball will strike the ground when dropped from center of bore at the muzzle at the same time a bullet fired parallel to the ground will hit the ground, modern bullets are aerodynamic, and they consistently strike the ground after one dropped from the muzzle.

[Jim Keenan]

Normally, the maximum bullet velocity is when the bullet exits the bore. Once that happens the pressure is gone and there is nothing that can accelerate it. The bullet then loses velocity due to air resistance, gravity pulls it down at the same rate as if it were dropped from the muzzle, and it strikes the ground if it hits nothing else first.

The reason I said "normally" is that if the powder charge is small enough and the barrel long enough, the gas pressure may be exhausted before the bullet leaves (or even reaches) the muzzle, so its maximum velocity was somewhere in the barrel.

Jim

[Apple a Day]

As the bullet leaves the barrel there is still more air pressure behind it than in front of it- it is still accelerating for a short distance. If the pressure inside the barrel were lower than the outside then when the bullet exited the barrel you'd hear a sucking noise as air rushed in to relieve the pressure difference instead of a BANG

There are some special 'silent' cartridges which are sealed and the casing has an odd plunger sort of arrangement which seals in the gas- kicks the bullet out of the barrel. I seem to remember the Russians having something like that. I will have to check some references. I assume you ain't talkin' about wunna them.

Gunpowder burns up making hot gas byproduct, which expands to relieve pressure difference- PV=nRT... good ol' combined Charles and Boyle's gas laws for those who went to "gummint skool" and studied chemistry. Atmospheric pressure is about 14.7 pounds per square inch. Until the gas in the barrel pushes the bullet out of the way and expands into enough volume and cools to reach atmospheric pressure then it is still pushing. You've probably got a couple of inches to maybe a foot before the pressures even out and the difference in air pressure runs the other direction and starts slowing it down, farther with a rifle.
Hard to measure with all the other matter banging out of the barrel.

[Mal H]

I suppose it's possible that the bullet will accelerate a little bit after it leaves the muzzle due to the still extreme pressure and speed of the gases pushing it and flowing past it (assuming enough powder in the load to create sufficient pressue all the way to the muzzle) and due to the friction of the bullet in the barrel dropping to zero. But, that acceleration would only be for a fraction of an inch if indeed it exists. After that short distance all the factors already mentioned take over. I'll bet someone has probably measured this or verified that it doesn't exist, most likely by high speed photography (Edgerton?). But, it's not commonly known if they have.

[Added]
Apple a Day and I were composing/posting at essentially the same time. I wouldn't be surprised if he is correct in his assumption of several inches, but it still isn't going to be a long distance.

[Zak Smith]

In 9mm from a 4" barrel, the pressure at the muzzle as the bullet exits will be around 3500-5000 PSI, or about an order of magnitude less than the peak pressure. Once there is clear space around the bullet base, the pressure will push the air there over the bullet since it is resistance.

-z

[dude]

While I most likely have no idea what I'm talking about, I will toss my 2 Rubles into the ring using my technical backround and skydiving expierence.

if F=MA, then A=F/M

A being Acceleration in distance/time
F being Force in '?"
M being Mass in weight units

P1 = V1/T1

V= 1/2 VT squared

(remember High school?)




it achieves max velocity (or rather speed) just before the resistance in front of the bullet is > the 'push' from behind. I'm no physicist (or speller) but I would have to assume that the bullet exiting the bore suddenly being relieved of the huge resistance from the barrel along with the ongiong blast rushing out of said bore will continue to accelerate the bullet for a time. This should happen not far from the bore but I am assuming there is a significant period of accereration in that short distance (it would be intresting to find out!)


As soon a pressure equalizes on either side of the bullet max speed will have been achieved and accelleration will stop as decelleration begins. Allthewhile after exiting the bore gravity will be pulling the bullet down at a constant rate (32' /sec/sec in a vaccume)..........methinks with little or no effect on acceleration.

Other than that I would have to say the bullet goes really (really) fast and I always hope to be behind them.

[JohnKSa]

Slightly more complicated than that...

It's also possible for the bullet to stop accelerating and begin to slow before it leaves the barrel. The friction between the barrel and the bullet is significant and if the pressure is low enough, or the bore is large enough or the barrel is long enough, the friction will win and begin to slow the bullet. I suspect that a very low powered round such as the 22CB might begin to slow in as little as 6" or less of barrel.

Assuming that is not the case, then maximum velocity will occur just slightly (inches?) after the bullet exits the muzzle.

As pointed out, the barrel/bullet friction is relieved as the bullet exits, but there are still high velocity, high pressure gases jetting out of the muzzle behind the bullet.

For all practical purposes, it is generally assumed that maximum velocity is at the muzzle.

[New_comer]

As soon as the bullet base is about 20.38 mils from the tip of the barrel...


How did I find out??


Don't ask ...:cool: :neener: :evil:

[Pistolsmith]

Well, here's the way to prove it to yourself once and for all. Now, who said that the Physics books were gospel? Seems to me, they avoid things they don't understand.
Lock a .45 acp pistol down in a Ransom Rest, pointing parallel to the ground and out over a patch of desert, where you can see the point of impact. Fire a reound with a H&G 68 bullet seated normally. Note impact point. Fire a similarly loaded round with the bullet seated backwards. Note that the flat end forward round hits the ground closer to the muzzle, thus proving that the bullet is aerodynamic when fired point end to. If you are really curious, obtain the NACA aircraft cowling outlines of 1929 from the Wright Pat Museum and compare them to Elmer Keith's 173 grain swc .38 special bullet. (Lyman 357429) Did he know what he was doing? Oh, yeah!
This is dangerous, but it resolves the debate once and for all.
We used a Florence style pyrex flask, mounted in a horizontal position with a bunsen burner under the round side of the bottom of the flask. Look through a box of new solid rubber stoppers until you find one that is a fairly tight fit in the neck from the start. Push it down into the neck until you have about 3/8" to 1/2" of bearing. Draw a line around the top of the neck position on the stopper. Then, sandpaper the topmost postion after wrapping sever wraps of tape around the bearing surface to the mark unti it will slip fit in the "bore" of the flask to the tape.
We used an old Bolex 8mm camera that took a 400 foot reel of film. (You only get to use 200', since you have to reverse the reels for the second half. Set at slow motion (64 frames per second.) Use a long cable release, a double thick sheet of plywood with a small window and a transparent section of thick lexan.
Watch the setup until the stopper begins to move and cramp down on the cable release.
Now, this is nothing like "real time", but proportionally, it is correct (who said "you can't scale nature"?) and when you have replayed the film for the umpteenth time, you will see the stopper speeds up appreciably when it exits the "bore" of the flask neck. It would help to place a sheet of cardboard behind the neck and in front with 1/2" spaced vertical lines to get a better appreciation of the differences in speed. You have a slow beginning, a faster exit and a marked accelleration.
This is dangerous, since the power of steam is nearly beyond imagination, but we did not have a tragedy using new Florence flasks and new stoppers.
And, none of this answers the original question, because a chronograph will not read muzzle velocity, but instead reads the shock wave of the report.
And, this poses the Zen question: "If nobody is present in the forest and a tree falls, does it make a crashing noise?" Answer: "No." When nobody is present, there is no phenomenon that we call "sound". It requires a receptor eardrum to convert the compressed air waves into perceptible sound, as it requires a radio receiver to convert the waves of a radio signal to audible sound when they reach your ear. (Not a precise analogy, but close enuf fer Gummint work. Again, let the skeptics rage. I have told all I know 'bout Newtonian Physics down a rifled tube.
In the final analysis, what difference does it make? It is still those little round (we hope) holes in the X ring that count. And, lotsa guys have fired millions of rounds without worrying about the physics involved. Just enjoy it.
Which, I guess, brings us back to cheating by slipping a rifle cartridge in a Lewis gun and quoting Savage. "30 to 35 feet per second accelleration past the muzzle due to impinging escaped gases."..unless somebody else can quote something different.

[trapshooter]

Set up series of laser traps, with adequate timing measurement for breaks, with lasers and receptors, timing equipment far enough back to eliminate muzzle blast damage, etc. Lock gun down solidly to eliminate movement that would allow bullet travel outside laser trap 'read' zone.

Fire gun. Look at time differences between traps.

At that point, it would all be clear.

[Pistolsmith]

Neat idea for those whose family have left them a million dollars. However, for most of us, we are stuck with a small chronograph that will not read muzzle velocity and the major loading manuals are deficit in this area. Therefore, nothing is clear and won't be until we get to see this laser data.

[dude]

physics ROCKS!

.........bullet areodynamics are taken into account at all phases of the fore/aft drag event

[trapshooter]

I had envisioned a multi-million dollar gov't grant, and access to all kinds of cool guns....

I would volunteer to be project bwana and test-shooter-in-chief, of course...:evil:

[Pistolsmith]

Trapshooter:
Perhaps you could sign on with Gun Tests; looks to me like they could use a new tester.

[Sven]

Possible exception:

A richocheting bullet fragment might actually travel at a faster velocity than did the original projectile, on account of having a lighter mass and a smaller effective cross-sectional area.

What do you think?

[Mal H]

Don't think so, Sven. Even in a 100% elastic bounce, there is nothing to give the fragment any additional impetus that would increase its velocity.

[JohnKSa]

A richocheting bullet fragment might actually travel at a faster velocity than did the original projectile, on account of having a lighter mass and a smaller effective cross-sectional area.
That won't work, but you could have a case where an impact causes a small chip to spall off the back of the object hit by the bullet. Under just the right circumstances, the chip could move faster than the bullet was going at impact.

[WESHOOT2]

Consider that gases exit the muzzle before the bullet..............

[Blackhawk]

Apple a Day got it, then others followed.

The gases behind the bullet are moving at the same speed until the bullet gets out of the way allowing them to really accelerate past it, which amounts to the bullet having a "tailwind" until they slow down enough to make the bullet plow through ambient air.

As for exactly what distance the bullet is fastest beyond the muzzle that is, it would be easier to calculate than to measure.

[Island Beretta]

There is actually continuing acceleration after leaving the muzzle. How much longer is dependent on wind conditions, bullet design, altitude of the shooter etc. Bear in mind that energy is never lost only transferred so in perfect conditions bullet slow-down is slow!! :cool:

[Pistolsmith]

Contemplate this: A bullet with a spitzer point (like metal penetrating) VS a full wadcutter. Air resistance acts to slow a bullet, at emergence from the muzzle until it strikes something solid, at varying rates, depending on nose shape, trailing edge shape, etc. All of the other physical forces mentioned also contribute to slowdown.
It occurs to me that some physicists believed that a bullet is of cylindrical, full wadcutter shape or at best a round ball. Whatcha think?
Furthermore, the Tower of Pisa gravitational experiment with a feather and a rock was predicated on dropping the feather quill first. If it is released flat, air resistance slows it appreciably, while it has much less effect on the rock, so the rock strikes first. Also, a good wind will perhaps deflect the rock slightly, but it can make the feather fly into the next city.

[Mal H]

It occurs to me that some physicists believed that a bullet is of cylindrical, full wadcutter shape or at best a round ball. Whatcha think? I can't, my brain hurts. :)

I have to admit, you lost me there, Pistolsmith. I don't see how any of the 3 paragraphs address the question asked. (BTW, Galileo used metal balls of different weights, not a feather and a rock. And his physical experiment may be myth, he presented it in a thought problem only, no evidence that he actually carried it out.)

[Pistolsmith]

I'm no Galileo, but I did the above experiment with the stated conclusions to prove what I'm saying about bullets being aerodynamic. Elmer said it in 1929; I'm just repeating what HE (not Galileo) said. Besides, I don't think the Eyties let Galileo own a gun, since the Pope made a very long and thorough investigation, then condemned him for his "damnable heresy". ...And him being infallible in all matters of faith and morals...oh, sorry he didn't declare himself infallible for a number of years yet..
I didn't do it at the Pisa tower, but the UPS tower looked right for the experiment, so I let 'er rip. Reporter for the school paper thought it was relevant, and it made page 1. Physics prof just groaned and rolled his eyes upward.
You sound like you never had any fun as a kid!
Did I ever tell you about the Physics instructor who was caught by a campus cop in the back seat of a Studebaker parked on the quad at 2 in the morning with one of his female students? Oh, sorry, that's totally irrelavant, like all of my other posts.

[Mal H]

You sound like you never had any fun as a kid! Not sure how you came to that particular conclusion, but you're pretty much 180 degrees out of phase. If you only knew ... :D :D

[griz]

I suppose it accelerates for a short while the gas is still pushing it, but it is a VERY short distance. When the base of a 9 mm bullet is about0.09 inches away from the barrel, the open area where the gas can escape is already equal to the area of the base of the bullet. We are talking small fractions of an inch, then the bullet starts slowing down.

It comes down to physics. I had a friend tell me that a baseball continues to accelerates for about a hundred feet after it leaves the bat. He couldn't name the force that did it, but he was sure because it looked like it had to in order to rise so fast. He was wrong. I'm not sure he thought the rules of physics applied in all cases.:rolleyes:

[WESHOOT2]

Looking at the March '95 Shooting Times article of high-speed photography capturing the firing of a Ruger P90.

I think it's over at the muzzle, me.

[Bill Adair]

I suspect a bullet, which is accelerating down the bore under intense pressure, continues to accelerate for a very short distance after exiting the muzzle. Not because the gasses are still pushing after it leaves the barrel, but because of the inertia of an accelerating mass.

The principle is simple physics. Items accelerating will continue to accelerate, until resistance overcomes inertia. If the bullet is still accelerating when it exits the muzzle, it will continue to accelerate for fractions of a second, until air resistance overcomes that acceleration, and velocity begins to decline.

We already know that barrel length effects muzzle velocity, and that in most cases a longer barrel will produce higher velocity, so we are pretty sure that the bullet is still accelerating, at least from most handgun, and short rifle barrels.

Measuring this would be very difficult (not impossible), with modern sensors. Getting someone to fund such testing might well be impossible! :D

I don't believe that gasses exiting the muzzle accelerate the bullet at all. The sudden drop in pressure when those gasses vent is almost instantaneous, thus the propelling force is lost.

There is also severe turbulence on the bullet as the gasses vent around it, which might possibly contribute to aerodynamic resistance, and reduce the velocity.

Bill

[Tim Burke]

The principle is simple physics.Apparently not.
From a Jr High School science project (http://www.aloha.com/~isaac/3laws/3lmid.htm), Newtons 1st law is: An object in motion tends to stay in motion, and an object at rest tends to stay at rest, unless the object is acted upon by an outside force.
It doesn't say an object accelerating will tend to accelerate.
The 2nd law is force = mass times accelleration.This can be expressed as F=ma, F/m=a or F/a=m. It is clear that if a mass is accelerating there is a force acting on it.

[Pistolsmith]

Think this one over: As the bullet exits the barrel, friction from the rifling is being reduced. From the exact time the parallel portion of the bullet begins to exit until the base has left the bore, there will be a miniscule INCREASE in velocity, since pressure remains behind it and friction is decreasing.
Perhaps a 9X23 Win caliber bullet would gain a bit from gas impinging at 45,000 psi, for a distanced measured in thousandths of an inch, but I'd seriously doubt that a .380 would be so increased.
As stated far above, the only PROVEN (i.e. DOCUMENTED) increase came from a Lewis gun firing .30-06 ammo.
You having fun yet?

[pogo2]

Sure the bullet accelerates after it leaves the barrel.

It accelerates toward the center of the earth due to the effect of the gravitational force on it.

Now in the direction of its travel, the bullet decelerates due to the force of air friction.

Think vectors.

[Pistolsmith]

And the rate of deceleration is directly proportional to bullet shape.
Also, a cloud of gas may well escape the muzzle BEFORE the bullet begins to protrude. (See Naramore's book "Principles and Practice of Reloading Ammunition" for a high speed photo of a Tommy gun barrel with the cloud of gas escaping as the bullet just begins to emerge from t he bore.)

[Dave R]

I believe that the RATE of acceleration changes as soon as the bullet leaves the barrel, but the bullet may continue to acclerate after it leaves the barrel, whether or not gas is pushing it.

Think about this. When you floor your car, and it is accelerating smartly, then you lift at peak acceleration...the _speed_ of the car will continue to increase for a short time, even thought the _rate_ of accleration drops as soon as you lift.

I think the same with bullets. If the bullet is still accelerating as it leaves the muzzle, it will continue to increase in speed for a short distance, even though the rate of acceleration begins dropping immediately.

[WESHOOT2]

:banghead: :banghead: :banghead:

Dave R,

mebbe..............

[Pistolsmith]

No offense, but your car continues to accellerate because you have gotten behind the power curve. Gasoline left in the carbuerator or in the injectors will continue to flow after release of th accellerator, albeit for a very short period of time, before it begins to slow down. When that happens on a 747, you belong to the ages.
Weshoot2: I'm not through with you yet. Look for my new post titled "More Ballistic Trivia." As the old sarge used to roar: "I didn't say you're dismissed...."

[MrAcheson]

Alrighty time for the engineer to speak up.

A few issues here. An supersonic bullet like a 9mm is travelling faster than the speed of sound (obviously). Pressure waves only propogate at the speed on sound unless something is pushing on them to go faster like the combustion of a propellant.

So the bullet leaves the muzzle. Its supersonic. The pressure wave pushing it is also supersonic because it is fueled by combustion and is constrained by the barrel. However once you leave the barrel it is no longer constrained (so the shape of the pressure curve changes) and the remaining powder burns up incredibly fast. So you have a very very short distance before the bullet is outrunning the driving pressure curve. So once the bullet is a fraction of an inch past the muzzle, it is going as fast as it ever will. Technically that is not the muzzle velocity but its so close it doesn't really matter.

As for the car and continue accelerating argument, no. Objects move at constant velocity (zero is a constant velocity) unless accelerated by a force. Your car keeps going faster because the engine hasn't stopped pushing the car yet.

[Blackhawk]

MrAcheson, you're a spoilsport. This could have gone on for many more pages and made my face hurt from smiling. :D

[Mal H]

:D
Me too, BH. I gave up several posts ago and just sat back smiling.

[Pistolsmith]

Mal:
Well, somebody hadda be there, or it would be a Physical THEORY and not a PHYSICAL LAW.
My regret is that you and I can't go back in time to watch Galileo drop his balls off the top of the tower of Pizza...(Does that sound right?) to see if they strike the ground at the same time. Only, we'd have to remember to take our Streamlites...it DID happen during the Dark Ages....

[Dave R]

It all depends on whether the bullet is still accelerating when leaves the muzzle. If the barrel is too long, and the propellant has burned and the bullet is decellerating, then of course it won't accelerate when it leaves the muzzle.

However......

If the bullet is accelerating when it leaves the muzzle (which I believe is the case in most pistols), it will continue to accelerate for some short time after it leaves the muzzle, as I said earlier. Here's why.

First, you need to differentiate between acceleration and speed. Just to use round numbers, lets assume the bullet is accelerating at the rate of 100fps per millisecond as it approches the muzzle. That is, every millisecond the bullet is going 100fps faster than the previous millisecond. At 8 ms its going 800fps, at 10ms its going 1000fps, etc. So that rate of 100fps per millisecond is the rate of acceleration.

Once it clears the muzzle, the rate of accelleration slows. So it goes from accelerating at 100fps per ms, to accelerating at 50 fps per millisecond, to accelerating at 25 fps per millisecond, to 0fps per millisecond. But it is still picking up speed during that process, even after it leaves the muzzle.

Then after it hits accleration of 0 fps per ms, it goes to -10 fps per millisecond, -25fps per ms, -100fps, etc. At that point it is losing speed.

So I don't know how far after the muzzle its rate of acceleration hits 0fps and it begins to slow, but it is still picking up speed after the muzzle, during that time that the rate of acceleration goes from 100fps per ms to 0 fps per ms.

Someone with better math skills than me can figure the distance out.

[MrAcheson]

Sorry Dave R but acceleration does not have to be continuous on the macro scale. If you want to be technical all forces are distributed in time and space so yes, acceleration must be continuous, but it is continuous on a time scale which is so small it doesn't matter. You are incapable of noticing it without multi-million dollar equipment. We are potentially talking about nano or picoseconds here.

Velocity does have to be continuous on the macro scale. According to newton's laws if no force is acting on an object, the object does not accelerate. Period. If a bullet accelerates any after it leaves the gun it means that a force, like residual pressure from the barrel, is accelerating it. Otherwise it is slowing down due to air resistance. This is fundamental physics.

[Dave R]

You convinced me, MrArcheson.

If the scenario I described were accurate--if you fire the bullet in space, where no no ther forces act on it after it leaves the muzzle, then the bullet would accelerate continuously. Nope.

Soon as it leaves the barrel, that's as fast as its gonna go. 'Cept maybe if the gas column pushes it a bit more after it clears the barrel.

Shoulda known that a real engineer would know more than a guy who once got an A in Physics 101.

[Mal H]

What MrAcheson said.

Dave your error is all contained in the one sentence: "Once it clears the muzzle, the rate of acceleration slows." As MrA said, acceleration can stop instantanously. There is no physical law that states that the rate must slow down, unlike velocity (when the body in motion is acted upon by a force vector in the opposite direction of its travel).

[Edit]
Nevermind. We were posting at the same time. I see you've figured out the error of your ways. :D

[ryucasta]

The attached file shows the calculated external ballistics for a 9x19 cartridge that’s configured for USPSA/IPSC Open Major.

[Mal H]

While interesting, that quicktarget chart doesn't help. The first increment is at 5 yds which is well beyond the fraction of an inch to a few inches where there might be some additional acceleration of the bullet.

[ryucasta]

Mal,

There are a lot of factors involved for example was a fast burning or slow burning powder used? What was the ambient temperature, atmospheric pressure, length of barrel, projectile material, powder charge, coating if any etc? Way too many variables anyway this thread reminds me of a debate that I read about from the middle ages where scholars debated how many angels could dance on the head of a pin.
;)

[Mal H]

You're certainly right about that!! Oh, and the answer is infinity.

[Blackhawk]

Define angel.

[Pistolsmith]

Define pinhead.

[db4]

The modern derivation of the medieval argument is: "How many dancing angels does it take to confuse a pinhead?"

If you think this is irrelevant today, you haven't been paying attention to politics.

[Kframe]

Someone brought up a question about an accellerated ricochet.

I bet it could happen.
If the ricochet is less of a bounce, and more of a bank, it may happen.
All it takes is an ever-tightening curve on a smooth surface.

Kinda like that ball-toss game with that curvey handled thing.
I had one as a kid.
I think it's based on that sport Jai A'lai or whatever the spelling is.
I'm thinking that it's actually like a lever.
The bullet or fragment would be "flicked" in the new direction.
I'm sure this doesn't happen often, but I think it could.
All it would take is the right angle at the right time.

Or am I wrong?

:) -Kframe

[Matt G]

Distance of max vel?

About 100 feet.








....For a GyroJet. ;)

[Tim Burke]

Touché!

[WESHOOT2]

Science has refuted the 'dropped same -- fall same" theory, with the more modern understanding that gravity acts on different mass differently.

Yep.

(Yes, I know this is not pertinent, but I wanted to impress all with my exceptional grasp of modern physics, and stuff.)