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Some More Ragging on Sectional Density

The information below is from this website and represents much effort by the author.  If you have not done this kind of work yourself, you cannot imagine the volume of work it takes for every individual shot.  As shooters and reloaders, we all owe a debt of gratitude to those who take the trouble and foot the bills.

The table below is the result of shooting at a 16kg  weight and measuring the distance the weight moves upon impact of the bullet.  It is in the order it was published originally.

Impact Test Results
Cartridge Distance Moved
in inches
Bullet Weight Velocity
in Ft. per sec.
Sectional Density
416 Rigby 19.5 400 grains 2400 .330
458 Winchester/
450 Nitro Express
22.75 500 grains 2150 .341
450 Ackley 30.5 500 grains 2400 .341
470 Nitro Express 27.25 500 grains 2150 .317
470 Mbogo 31.25 500 grains 2500 .317
470 Mbogo (Woodleigh Solid) 32.875 500 grains 2500 .317
500 Nitro Express 33.5 600 grains 2150 .330
505 Gibbs 27.5 525 grains 2300 .288
500 Jeffery 29.75 525 grains 2400 .288
500 A-Square 49.5 600 grains 2400 .330

Below,  the table is rearranged in order of shortest distance the weight was moved to furthest distance moved. It becomes very clear that sectional density has nothing to do with the force imparted to this particular target by the bullets striking it. The sectional density column could not be a more random collection of results. The addition of momentum and energy columns, show a set of numbers that bear much closer relationship to the test results. With only one anomaly in the momentum column,  within the variance one can expect with this type of test and probably the result of differences in bullet shape, muzzle pressure and bullet behaviour in the impacted medium, it seems that momentum is the clue to how far a weight can be pushed with a fired bullet.

Impact Test Results
Cartridge Distance Moved
in inches
Bullet Weight Velocity
in Ft. per sec.
Sectional Density Momentum Energy
416 Rigby 19.5 400 grains 2400 .330 137.1 5117
458 Winchester/
450 Nitro Express
22.75 500 grains 2150 .341 153.6 5133
470 Nitro Express 27.25 500 grains 2150 .317 153.6 5133
505 Gibbs 27.5 525 grains 2300 .288 172.5 6168
500 Jeffery 29.75 525 grains 2400 .288 180 6716
450 Ackley (Hornady solid) 30.5 500 grains 2400 .341 171.4 6397
470 Mbogo 31.25 500 grains 2500 .317 178.6 6941
470 Mbogo (Woodleigh Solid) 32.875 500 grains 2500 .317 178.6 6941
500 Nitro Express 33.5 600 grains 2150 .330 184.3 6160
500 A-Square 49.5 600 grains 2400 .330 205.7 7676

The table below lists the results of shooting into layers of plywood.  The original data was also published at 470Mbogo.com and not arranged in order of lowest to highest penetration.  If the results are aranged in order of lowest penetration to highest, the results become somewhat confusing.  No single factor seems to be linked to the depth of penetration.

Plywood Penetration Test Results
Cartridge Plywood Penetration Bullet Weight Velocity
in Ft. per sec.
Sectional Density Momentum Energy
470 Nitro Express 57 500 grains 2150 .317 153.6 5133
505 Gibbs 60 525 grains 2300 .288 172.5 6168
500 Jeffery 62 525 grains 2400 .288 180 6716
500 Nitro Express 62 600 grains 2150 .330 184.3 6160
458 Winchester/
450 Nitro Express
66 500 grains 2150 .341 153.6 5133
416 Rigby 71.5 400 grains 2400 .330 137.1 5117
470 Mbogo 72 500 grains 2500 .317 178.6 6941
500 A-Square 73 600 grains 2400 .330 205.7 7676
470 Mbogo (Woodleigh Solid) 90 500 grains 2500 .317 178.6 6941
450 Ackley (Hornady) 92 500 grains 2400 .341 171.4 6397

Anyone who has experience of the performance of the tested cartridges in game, will see that the plywood penetration results bear little relationship to the practical application of these cartridges to game. The wood penetration also shows no relationship to sectional density, momentum, energy, speed or caliber. When comparing cartridges and bullets for hunting, wood and similar media testing is interesting, but of no interest, as the medium is too different from tissue and bone.

Based on the last table, a direct comparison of penetration and sectional density in the chart above, shows that any link between the two is imaginary, as are comparisons of penetration to speed or momentum or energy.   Terminal performance is a highly complex subject and an interaction of a multitude of factors.  The closest one could probably come to a single factor for gauging terminal performance, is Momentum/Cross Sectional Area (Mo/XSA) and then only if the numbers are tempered with bullet shape, bullet construction and the effect of speed induced stagnation pressure.

The bottom line is that, choosing between two bullets based purely on sectional density, is as foolish as choosing a bullet based on the colour of the packaging.

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GS Custom Bullets, situated in Port Elizabeth on the East Coast of South Africa, manufactures solid copper, turned, monolithic bullets for hunting and sport shooting. These bullets are used by hunters on several continents, hunting from the smallest of antelope to the largest of dangerous game, using the smooth HP bullet, as well as the more popular HV, FN and SP bullets with the patented drive band concept. GSC bullets are configured for the highest possible ballistic coefficients. SP bullets are mainly used for sport shooting. All GS Custom Bullets are moly coated.