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#### JustinTrav

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Im currently enrolled in a gunsmithing school and have an assignment to reach out to people with experience in firearms and get their explanation and definition on some basic ballistic characteristics. Can someone please explain to me what is Trajectory, Wind Drift, Recoil, Velocity and Accuracy.

Also could you give two examples for calculating either Bullet Energy, Sectional Density, Telescopic Sight Adjustments or Correcting Factory Velocity for barrel length?

Any and all help would be greatly appreciated.

#### G66enigma

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Here's one resource to get you started on the basics.

Big Book of Ballistics, by Philip Massaro. A GunDigest publication.

#### JustinTrav

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#### c3shooter

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Bullet energy is calculated by mass of the bullet in grains, multiplied by speed in fps, squared- then divided by 450240 (a constant for changing energy to foot lbs). lets say you have a 100 grain bullet, moving at 1000 fps. 1000 times 1000= 1,000,000- times 100= 100,000,000, then divided by 450240= 222.10 foot lbs of energy.

Velocity is the speed of the projectile. It will be influenced by the pressure of expanding gasses, how long they have to push on the bullet (barrel length), the density of air it passes thru (altitude, temperature and humidity) and how efficiently the bullet can slip thru the air (the ballistic co-efficient of the bullet)

Factory velocity is right up there with unicorns and leprechauns. The factory uses a "test barrel" that is frequently longer than a standard barrel. A useful website called Ballistics by the Inch has tables of the velocity of a number of makes and weights and calibers- shown in different length barrels.

Trajectory is simply the curved path (by gravity, wind, and in extreme long ranges, rotation of the earth) that the bullet follows thru the air. Wind drift is when a wind blowing against the side of a bullet shifts the bullet over. A wind blowing from 3 o'clock will push the bullet toward 9 o'clock. Recoil- for every action, there is an equal and opposite reaction. Recoil is equal to bullet energy- 1000 ft pounds to the bullet= 1000 ft pounds to the gun. However, things like muzzle brakes can use some of the energy from waste gasses to counter some of the recoil.

#### JustinTrav

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Bullet energy is calculated by mass of the bullet in grains, multiplied by speed in fps, squared- then divided by 450240 (a constant for changing energy to foot lbs). lets say you have a 100 grain bullet, moving at 1000 fpf. 1000 times 1000= 1,000,000- times 100= 100,000,000, then divided by 450240= 222.10 foot lbs of energy.

Velocity is the speed of the projectile. It will be influenced by the pressure of expanding gasses, how long they have to push on the bullet (barrel length), the density of air it passes thru (altitude, temperature and humidity) and how efficiently the bullet can slip thru the air (the ballistic co-efficient of the bullet)

Factory velocity is right up there with unicorns and leprechauns. The factory uses a "test barrel" that is frequently longer than a standard barrel. A useful website called Ballistics by the Inch has tables of the velocity of a number of makes and weights and calibers- shown in different length barrels.

Trajectory is simply the curved path (by gravity, wind, and in extreme long ranges, rotation of the earth) that the bullet follows thru the air. Wind drift is when a wind blowing against the side of a bullet shifts the bullet over. A wind blowing from 3 o'clock will push the bullet toward 9 o'clock. Recoil- for every action, there is an equal and opposite reaction. Recoil is equal to bullet energy- 1000 ft pounds to the bullet= 1000 ft pounds to the gun. However, things like muzzle brakes can use some of the energy from waste gasses to counter some of the recoil.
Thats great info and consistent with what I have read so far. Just needed to have a person to reference similarities and differences in my findings for my assignment.

#### c3shooter

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Justin- does your gunsmithing course discuss the effects of gunpowder and steel on causing alterations in the flow of time? Just ask anyone that has taken a gun to a gunsmith, and been told "It'll take about 2 weeks". That is a sure sign that the flow of time is about to be changed, and slowed down dramatically.

woodlander

#### JustinTrav

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Justin- does your gunsmithing course discuss the effects of gunpowder and steel on causing alterations in the flow of time? Just ask anyone that has taken a gun to a gunsmith, and been told "It'll take about 2 weeks". That is a sure sign that the flow of time is about to be changed, and slowed down dramatically.
I honestly have no idea at this point. This was my first week of class of the start of the 14 month program. It through Sonoran Desert Institute

#### c3shooter

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Justin- about the time thing- just kidding. Sometimes I may pull your leg, only to have it come off.

Sectional Density (of a bullet) is the weight of the bullet divided by the square of the bullet diameter. Gives a simple number than can give an understanding of the effectiveness of a given bullet. Some reading for you HERE: Sectional Density for Beginners (chuckhawks.com)

A .308 Winchester could be loaded with several different bullets- all the same diameter, but VERY different weights. There are loads as light as 110 grains, as heavy as 220 grains. The 110 would be good for plinking at varmints. The 220 can plant a moose. But the 110 grain used on a moose........... yeah, don't plan on a good outcome.

DHall_37

#### tac foley

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Thats great info and consistent with what I have read so far. Just needed to have a person to reference similarities and differences in my findings for my assignment.
The laws of physics have no similarities or differences, that is why the laws of ballistics are called the laws of ballistics. No matter who squeezes the trigger, and no matter what he or she is shooting at, or with, the rules governing the calculation of the ballistic performance of any projectile are the same.

What exactly are you asking us to do?

#### HydroR

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Accuracy - the relationship of the impact point to the desired impact point.

Accuracy is tied to precision. Precision is the relationship of multiple impact points to each other (grouping).

You can have high presicision (very tight groups), but poor accuracy (hitting several inches away from the bullseye), for example.

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Nailed.

#### tac foley

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I have to ask if the OP has actually fired a real, live honest to goodness firearm. The explanation for recoil would then be much easier to comprehend.

We ALL experience recoil at a different level - some seem to be immune, and some, like me, seem to enjoy it [mostly] as a sign that the gun is working.

Total lack of recoil is something else.

It usually means that your gun is empty.

In any case, the OP could spend a few happy evenings watching people shooting on Youtube - AKA 'the students' friend' - to see all this.

Meanwhile, he seems to have buggered off left.

#### Chainfire

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I have to ask if the OP has actually fired a real, live honest to goodness firearm. The explanation for recoil would then be much easier to comprehend.

We ALL experience recoil at a different level - some seem to be immune, and some, like me, seem to enjoy it [mostly] as a sign that the gun is working.

Total lack of recoil is something else.

It usually means that your gun is empty.

In any case, the OP could spend a few happy evenings watching people shooting on Youtube - AKA 'the students' friend' - to see all this.

Meanwhile, he seems to have buggered off left.
There would not be a total lack of recoil when firing, even if the gun wasn't loaded.....

#### tac foley

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There would not be a total lack of recoil when firing, even if the gun wasn't loaded.....
?

#### HydroR

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Imperceptible, perhaps, but the striker/hammer would cause some when it is "launched" and when it hits the firing pin.... measurable with the right instruments. Newton's third law.

#### tac foley

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Imperceptible, perhaps, but the striker/hammer would cause some when it is "launched" and when it hits the firing pin.... measurable with the right instruments. Newton's third law.
Imperceptible to a human squeezing the trigger, IOW.

#### HydroR

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Wellll....if you consider the the little click you feel when the striker/hammer hits in dry firing, then I guess arguably it is perceptible. We just don't think of it as "recoil" in the classic sense, but there is perceptible movement.

#### tac foley

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I think our little 'wossitlike' buddy is thinking about something like this.........

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