KIPR - Karcher Impact Performance (Refined)
About KIPR - KIPR was the culmination of trying to improve upon an old, and dare I say outdated, method of cartridge comparison. It started out as KIP, or Karcher Impact Performance, but as I tweaked the formula a bit to achieve smoother and more useful results, it morphed into KIPP (Karcher Impact Performance, Precise) and as of the latest iteration, KIPR. The idea is to compare not just bullet diameter and weight and velocity, but also include sectional density into the equation. KIPR also uses frontal area, in place of diameter.
This is far from a perfect equation, and at the end of the day, a successful hunt will always come down to shot placement over all else, but for those of us that like to get into the nerdy side of things, it’s an interesting way to compare cartridges, and as far as I know this is the first of such an equation formulated in the 21st century.
EDIT 10 NOV 2025:
It has come to my attention that there HAS, in fact, been several formulas, such as the KPS formula, developed by the late Chuck Hawks. Our formulas differ very slightly, with both using energy, sectional density, and frontal area to assign a number to a given cartridge and load. Mine is a little bit more friendly towards the smaller/weaker cartridges by assigning numbers above one to even a .22 LR (4.4 KIPR) whereas the KPS would assign it a .44 if calculated the same way.
Provided here is a list of various cartridges and loads for comparison purposes.
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55GR @ 3200 ft/sec
Kinetic Energy (Imperial): 1250.89 ft-lbs, (Metric): 1695.98 joules
Sectional Density (Imperial): 0.158 lb/in², (Metric): 111.1 kg/m²
Frontal Area (Imperial): 0.0391 in², (Metric): 0.0000252 m²
KIPR Score: 77.19
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77GR @ 2800 ft/sec
Kinetic Energy (Imperial): 1340.8 ft-lbs, (Metric): 1817.88 joules
Sectional Density (Imperial): 0.221 lb/in², (Metric): 155.5 kg/m²
Frontal Area (Imperial): 0.0391 in², (Metric): 0.0000252 m²
KIPR Score: 115.84
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80GR @ 3350 ft/sec
Kinetic Energy (Imperial): 1994.05 ft-lbs, (Metric): 2703.57 joules
Sectional Density (Imperial): 0.194 lb/in², (Metric): 136.1 kg/m²
Frontal Area (Imperial): 0.0464 in², (Metric): 0.00002992 m²
KIPR Score: 178.99
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100 GR @ 2960 ft/sec
Kinetic Energy (Imperial): 1945.98 ft-lbs, (Metric): 2638.4 joules
Sectional Density (Imperial): 0.242 lb/in², (Metric): 170.1 kg/m²
Frontal Area (Imperial): 0.0464 in², (Metric): 0.00002992 m²
KIPR Score: 218.34
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127 GR @ 2825
Kinetic Energy (Imperial): 2251.11 ft-lbs, (Metric): 3052.09 joules
Sectional Density (Imperial): 0.26 lb/in², (Metric): 183 kg/m²
Frontal Area (Imperial): 0.0547 in², (Metric): 0.00003532 m²
KIPR Score: 320.77
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140 GR @ 2675
Kinetic Energy (Imperial): 2225.01 ft-lbs, (Metric): 3016.71 joules
Sectional Density (Imperial): 0.287 lb/in², (Metric): 201.8 kg/m²
Frontal Area (Imperial): 0.0547 in², (Metric): 0.00003532 m²
KIPR Score: 349.5
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130 GR @ 3000 ft/sec
Kinetic Energy (Imperial): 2598.61 ft-lbs, (Metric): 3523.25 joules
Sectional Density (Imperial): 0.242 lb/in², (Metric): 170.2 kg/m²
Frontal Area (Imperial): 0.0603 in², (Metric): 0.00003888 m²
KIPR Score: 379.03
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150 GR @ 2850 ft/sec
Kinetic Energy (Imperial): 2706.06 ft-lbs, (Metric): 3668.92 joules
Sectional Density (Imperial): 0.279 lb/in², (Metric): 196.4 kg/m²
Frontal Area (Imperial): 0.0603 in², (Metric): 0.00003888 m²
KIPR Score: 455.43
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140 @ 2950 ft/sec
Kinetic Energy (Imperial): 2706 ft-lbs, (Metric): 3668.85 joules
Sectional Density (Imperial): 0.287 lb/in², (Metric): 201.8 kg/m²
Frontal Area (Imperial): 0.0547 in², (Metric): 0.00003532 m²
KIPR Score: 425.06
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140 GR @ 3050 ft/sec
Kinetic Energy (Imperial): 2892.55 ft-lbs, (Metric): 3921.77 joules
Sectional Density (Imperial): 0.287 lb/in², (Metric): 201.8 kg/m²
Frontal Area (Imperial): 0.0547 in², (Metric): 0.00003532 m²
KIPR Score: 454.36