The Los Angeles Handgun - Rifle - Air Pistol Silhouette Club

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Ballistic Formulas / Conversion Tables / Notes

     

Loads Per Pound of Powder

Weight / Length Equivalents Conversion Factors

Powder    

   Loads Powder

Loads

       Powder Loads    
5 gr. = 1400 40 gr. = 175 75 gr. = 93 7000 Grains = 1 Pound Pounds  x 7000 = Grains
10 gr. = 700 45 gr. = 155 80 gr. = 87 437.5 Grains = 1 Ounce Ounces  x 437.5 = Grains
15 gr. = 466 50 gr. = 140 85 gr. = 82 15.43 Grains = 1 Gram Grains  x .00229 = Ounces
20 gr. = 350 55 gr. = 127 90 gr. = 77 25.4 Millimeters = 1 Inch Grams  x 15.4324 = Grains
25 gr. = 280 60 gr. = 116 95 gr. = 73   Grains  x .0648 = Grams
30 gr. = 233 65 gr. = 107 100 gr. = 70   Inches  x 25.4 = Millimeters
35 gr. = 200 70 gr. = 100         Millimeters  x .03937 = Inches

Common Abbreviations

 

ACP > Automatic Colt Pistol HPBT > Hollow Point Boat Tail SAA > Single Action Army
AV > Average Velocity HS > Hydra Shok HP (Federal) SD > Sectional Density or
BB > Bevel Base J > Jacketed Bullet     Standard Deviation
BBWC > Bevel Base Wadcutter JHC > Jacketed Hollow SIL > Silhouette
BC > Ballistic Coefficient        Core/Cavity SJ > Short Jacket
BP > Bullet Pull JFP > Jacketed Flat Point SP > Spire Point / Soft Point
BPS > Black Powder Silhouette JHP > Jacketed Hollow Point SWC > Semi-Wadcutter
BR > Bench Rest KEITH > Elmer Keith Bullet Design SSP > Single Shot Pistol
BT > Boat Tail L/LB > Lead Bullet TC > Truncated Cone
CAV > Cavalry LBT > Lead Bullet Technology T/C > Thompson Center Arms
CB > Cast Bullet LD > Loading Density TMJ > Total Metal Jacket
CF > Center Fire LOS > Line of Sight TOF > Time of Flight
CV > Coefficient of Variation LRN > Lead Round Nose WC > Wadcutter
CUP > Copper Units of Pressure MC > Metal Case WCF > Winchester Center Fire
DCM > Dir. Civilian Marksmanship ME > Muzzle Energy WLN > Wide Long Nose (LBT
FMJ >    Full Metal Jacket MOA > Minute of Angle           bullet design)
FN > Flat Nose MR > Mean Radius XTP > Extreme Terminal
FP > Flat Point MV > Muzzle Velocity          Performance, (Hornady jacketed
FPS > Feet Per Second NSS   North-South Skirmish          hollow point)
GC > Gas Check OAL > Over All Length      
HBWC > Hollow Base Wadcutter PSI > Pounds Per Square Inch      
HJ > Half Jacket R/RB > Round Ball      
HP > Hollow Point RF > Rim Fire      
      RN > Round Nose      

 

Associations / Organizations Abbreviations

Is Your Range In Meters Or Yards?
CBA > Cast Bullet Association   Multiply:        

Abbreviations

CCA > Colt Collectors Association   Yards By 0.9144 To get Meters

FPS

> Feet Per Second
IHMSA > International Handgun Metallic Silhouette Association   Meters By 1.094 To get Yards

MPS

> Meters Per Second
IPSC > International Practical Shooting Association   FPS By 0.3048 To get MPS

MPH

> Miles Per Hour
NBRSA > National Bench Rest Shooters Association   MPS By 3.281 To get FPS

 

NRA > National Rifle Association   FPS By 0.6818 To get MPH  
NRMA > National Reloading Manufacturers' Association              
NSSF > National Shooting Sports Foundation            
SAAMI > Small Arms and Ammunition Manufacturers Institute            
SASS > Single Action Shooters Society            
USPSA > United States Practical Shooting Association          

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Greenhill Formula
      The formula to determine the correct rate of rifling pitch for bullets of usual construction (lead alloy or jacketed) is known as the "Greenhill Formula".
Step One: Determine the length of the bullet in calibers. (Bullets length in inches divided by the bullets nominal caliber).
Step Two: Divide 150 (a constant) by the bullets length in calibers.
Step Three: Multiply the result of step two by the bullets "nominal" caliber. This will give the desired rifling twist rate.
     Example: To find the correct twist for a .30 caliber 220 grain bullet 1.35 inches long.

1.35

  150   33.33 x .30 = 9.999

.30  

= 4.5 calibers 4.5

= 33.33

(or 1 in 10 inch twist)

Muzzle Energy   Momentum In Pound Seconds
      Weight of bullet (in grains) x velocity (in foot seconds) x velocity x 0.000002218 = energy in foot pounds. *       Multiply the bullet weight in grains by the velocity at impact. Divide the product by 226,000 ( a gravimetric Constant).
Example: 100 grain bullet at 3000 ft/seconds > 100 x 3000 x
3000 x 0.000002218 = 1996 foot pounds energy. * Example: 45 caliber 240 grain bullet 200 yard velocity of 985 fps. 240 x 985 = 236400 divided by 226,000 = 1.046 pound-seconds momentum.
 

Standard Deviation   Coefficient of Variation
     Example: 5 shot string, velocity's of 1020, 980, 1000, 1015, 985. First, add the five velocity's and take their average: 1020, 980, 1000, 1015, 985 *       The coefficient of Variation shows the standard deviation as a percent of the average and is a more reliable measure of a loads consistency.
The five velocity's add up to 5000 fps. Their average is 1,000 fps (5000/5) Next subtract the average from each velocity and square the difference. Add up the squared differences (1250) and divide by 4 (the number of velocity's minus one). *

The smaller the CV the less variation there is "relative to the average". Divide the average into the standard deviation and multiply the result by 100. From the above example of standard deviation: The S.D. is 17.68. The average is 1000.

Always divide the number of measurements minus one. The result is 312.5 or 17.68: (17.68 x 17.68 = 312.5). *      Example: 17.68 (SD) divided by 1000 (velocity) = 0.01768 x 100 = 1.768. The CV is 1.768.

Sectional Density
The formula for SD is: SD = WG /7000 x D2
Where WG is weight is in grains and D is is the bullets diameter in inches.
     Example:  For a 180 grain .30 caliber bullet, SD = 180/7000 x .308 squared. Divide the bullets weight in grains (180) by the number of grains in a pound (7000), which yields .2571428. Next square the bullets caliber in inches (.308 x .308) which gives .094864 and divide into .2571428 which yields .2710638. This rounds off to an SD of  .271.
 
 
     
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