What is the best all around rifle cartridge for a large bore rifle? Also, what is the best test to determine that top candidate? I would like to expand on a statement by Finn Aagaard (Safari Rifles, Craig Boddington – Pg 378), where he says, "I have never been able to detect any difference in the field on game, between the .458 and .500/.450, .465, .470, or even the .500 Nitro Express."
OK, maybe just another man’s opinion, but it is a concept I combined with another author’s remarks declaring that a bullet with the sectional density of .300 and a starting velocity near 2000 fps or better, is needed to take down an elephant (Richard Harland, NDLOVO The Art of Hunting the African Elephant, page 380). So, I came up with the following theory.
Sectional Density times Velocity, for solid rounds, appears to be the universal equation that levels the playing field and removes all the voodoo, folklore, and literary romance from the discussion. This value to me is the clearest penetration calculation check of a caliber encompassing mass, cross sectional area, and velocity.
This value stops short of John Taylor’s theory in creating a KO factor.
Taylor’s factor is Bullet Mass in grains, Velocity in feet per second and Bullet Diameter in inches multiplied together then divided by 7000. A 30-06 has numbers near 21, 375 H&H around 41, 416 Rigby at 57 and a 458 Win Mag comes in at 70.
These values are of a general nature (bullet weights and velocity) to indicate the step increase in the cartridge’s power levels, and show the brilliance of John Taylor in his time.
His life experience, in taking large numbers of game and being able to correlate his values to his field observations, is something few have attempted. In this case, the bullet diameter is a plus as a larger bore rifle firing an equivalent bullet weight at the same velocity is a better "thumper" based on Taylor’s calculation.
Regarding this analysis of penetration, the opposite is true with a bullet of higher sectional density hence a smaller diameter for the same given weight and velocity will provide better penetration results.
Listed below is a small sampling I have put together comparing some of the common African rounds with some general velocities and bullet weights.
The benchmark I use is the 470 Nitro as my years of reading found no abusive language and this caliber found in the same sentence; it is a saint.
The Section Density times Velocity target value is 682.
A comparison of the numbers supports Mr. Aagaard statement with most rounds equaling or exceeding 682. I also looked at 458 Win Mag in detail by dropping the velocity and found I could match the 470 Nitro at 2000 fps and match the 505 Gibbs penetration factor at 1950 fps.
I started with the .338 caliber as I have come across a number of articles with the 338 Win Mag being used on Lion and Cape Buffalo very successfully and I personally own one. Top honors go to the 375 H&H, 416 Rigby, and 458 Lott - showing why they can take large game at almost any angle.
The winner is the 338 Win Mag based on this comparison, a true scalpel in the hands of a professional using the 275 Tungsten African Grand Slam bullets. Unfortunately, Speer no longer makes these.
I will concede that the 338 lacks the frontal area of the 375+ calibers (even the 375 is the questionable at times) to be regarded as any type of charge stopper, but with proper shot placement dispatch anything it is pointed at.
I was also able to locate a wonderful set of test data, "Comparing the Big Bores" by Dave Estergaard (http://www.470mbogo.com/BigBores/BigBores.html), where he used penetration of ¾ inch plywood planks to compare the following rounds.
Adding a column to evaluate the Sectional Density times Velocity factor, we have the following table:
Graphing Bullet Diameter vs. (Sectional Density times Velocity Factor)
Graphing Bullet Diameter vs. Plywood penetration.
These two graphs have striking similarities, which lets me know we are on the right track, so I went to the next level and graphed our Sectional Density times Velocity Factor vs. plywood penetration, and came up with a correlation coefficient of 0.74.
Not bad, but the 458 Ackley data appeared to be a little off, so I recalculated the data again minus the Ackley and came up with a respectable correlation coefficient of 0.94.
In conclusion, this data is not taken from animal shots in tissue and bone, nevertheless it appears to be a relative simple and effective tool for estimating bullet penetration in game. Finn Aagaard’s statement, "I have never been able to detect any difference in the field, on game, between the .458 and .500/.450, .465, .470, or even the .500 N.E." – from my data is fair, reasonable, and accurate. The 505 Gibbs was a surprise, coming in very near the bottom in both calculated factor and plywood penetration – maybe bigger is not always better.
The leader in this penetration analysis is the 338 Win Mag and a challenge to the 375 H&H for the all around title for best cartridge. In most of my readings of African cartridges, time and time again I come across words of respect for the 318 Westley Richards and 333 Jeffery (African Rifles and Cartridges by John Taylor, Chapter 5, The Medium Bores). Medium calibers with a light report are not charge stoppers, but with a good solid bullet, they can leave four pachyderm or bovine feet pointed towards the blue sky.
Three Cheers for Finn.