Shotgunworld

ezOP

Posts: 61

(10/19/00 11:52:28 pm)

Sabot slug trajectory info

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Hello Richard,

Thanks for visiting Shotgunworld.com

I wasn't able to find any trajectory info on the sabot slugs. The best I

could do was provide some links that might be helpful.

Winchester's slug info is at

www.winchester.com/products/main.cfm
Software for calculating the ballistics is at Loadammo.com

www.loadammo.com/ . Make sure that it supports shotgun slugs before

you buy it.

You download a demo copy at

www.loadammo.com/regdemo.htm
I've also included a very informative article at the end of this email

Federal has a very good (and free) ballistics program you can download at

www.federalcartridge.com/kndex.html
that may help.

Their Sabot slug info is at

www.federalcartridge.com/.../specs2.pl
You can find some neat info on sabot slugs at

www.mpbpolywad.com/qs12ga.html
Hope it helps.

regards,

Jay Gentry

Shotgunworld.com

How a ballistics program works

-or how to calculate a trjectory chart-

by: R White

Up front I should say that this information is based on how The

Shootist, version 2.21, works, and there are other ways of obtaining the

information contained in a firing table. I should also set up some

definitions to keep the confusion down.

A ballistic table generally does not contain information about a

particular projectile's trajectory, but rather general information on the

flight of projectiles. The table is then used in conjunction with a set of

formulas to produce the trajectory information. Generally, a trajectory

chart

is computed in the following way:

1] Find the remaining velocity and time of flight to the range in

question.

2] Find the drop of the projectile using this information.

3] Correct for the zero of the firearm in question.

All other information, such as kinetic energy or energy transfer, may

be found using the information from these calculations.

Part I: Remaining velocity and time of flight.

A table and formulea for using it are included in the file Ingall.txt

which may be printed out for convenience in use. This table and its

formulea are derived from the Ingall's ballistic tables. These tables were

founded upon the test firing of some 'standard' projectiles, and the

resulting

calculations must be corrected with 'ballistic coefficients.' This is

simply

a measure of the difference in air resistance between the 'standard

projectile'

used in compiling the table and an ordinary, common, bullet.

Why is a table used instead of a straight formula? Because it was

found by many scientist doing ballistics test that a bullet does not lose

speed uniformly. The rate of velocity loss is dependant upon a combination

of many factors making the formulea for computing velocity loss very

difficult and complicated. The main factor is the sound barrier; bullets

lose velocity at a different rate above and below it.

Part II: Find the drop of the bullet.

This is done also on a table, but can be accomplished with formulas.

The table used in The Shootist is once again included in the file

Ingall.txt.

It is based upon the premise that all objects fall at a given rate:

2

Drop (inches) = 193 x (time of flight)

Inherent inaccuracies occur, however, in the formula because of

wind resistance, which actually works to slow down the fall of the bullet.

The action of the air has already been computed into the table.

Instructions

on the tables usage are also included. An explination of the formulea

involved in calculating the effect of the air resistance can be found in

"Exterior Ballistics" by McShane (and others). The table The Shootist

uses is one shown in "Hatcher's Notebook," which is derived from the one in

"Exterior Ballistics. To show how much difference there is when the air

resistance is figured in, the following comparison is made:

Yards 100 200 300 400

With 1.8 7.5 17.7 33.6

Without 1.93 7.72 19.76 37.36

This is based on a bullet beginning at 3200 fps with a ballistic coefficient

of .44. The 'With' row was calculated using the table provided in

Ingall.txt,

while the 'Without' was calculated with the formula given above.

Part III: Correct for the sighting in of the firearm.

This involves a bit of trigonometry that will not even feel like

trigonometry:

H is the height of the sight above the bore

D is the drop in inches of the bullet at sight-in range

S is the sight in range in inches

R is the range in question in inches

I is the drop from the bore at the range in question

T is the difference in inches from the line of sight

If the range in question is less than the sight in range

T = (D-I) - ((S-R) x ((D+H)/S)

If the range in question is more than the sight in range

T = (D-I) + ((R-S) x ((D+H)/S)

The sight in range is not covered by either of the two formulea

becuase it is known to be 0.

For example:

A bullet fired from a gun sighted in at 200 yards drops 4.2 inches

in its first 100 yards of travel. How many inches is it above the line of

sight? The drop from the bore at the sight in range is 7.5 inches (these

are calculated from the tables).

T = (D-I) - ((S-R) x ((D+H)/S)

T = (7.5-1. - ((7200-3600) x ((7.5+1.5)/7200)

T = 5.7 - (3600 x .00125)

T = 5.7 - 4.5

T = 1.2 inches (above the line of sight)

Another:

The same bullet drops 17.7 inches by 300 feet. How far off the line

of sight is it now?

T = (D-I) + ((R-S) x ((D+H)/S)

T = (7.5-17.7) + ((10800-7200) x ((7.5+1.5)/7200)

T = -10.2 + (3600 x .00125)

T = -10.2 + 4.5

T = -5.7 inches (below the line of sight)

Other Formulas:

2

Kinetic Energy = ((Bullet wght/22521 x Velocity )/2

Energy Transfer = Kinetic Energy x Caliber

3 2

Optimum Game Weight = Velocity x Bullet Weight x 1.5012 x 10e-13

Mach = Velocity/1127

Miles per hour = (Velocity x 3600)/5280

Wind drift:

t = time of flight in seconds

s = wind speed in mph

a = angle of wind off trajectory path

v = muzzle velocity in feet per second

r = range in yards

Wind drift = (s x sin(a)) x (t - (v/r)

I know all this is a bit complicated, but with a little practice it

becomes rather easy to make the computations necessary. For further

information read "Hatcher's Notebook," which covers a lot of other

interesting territory besides exterior ballistics. If you have any

questions,

leave me a message on CompuServe's NRA forum.

Russ White