Ballistic Coefficients Do Not Exist!
This may sound puzzling to some, but ballistic coefficients, as typically applied to muzzleloading projectiles, are never, ever an accurate representation of retained velocity and kinetic energy--in your gun, with your specific load, at any random distance that you might harvest your game animal. This jumbled, majestic mystery of ballistic baloney has been perpetrated on the innocent muzzleloading public, in large measure, by the affable Baron of Bullets and Lord of Lead himself, Mr. Cecil Epp, of Precision Rifle Custom Muzzleloading Bullets.
A little history is in order. The black powder community, over the years, has paid scant attention to ballistic coefficients: the ability to swim through the air as compared to the "C" bullet that Krupp, of Germany, defined in 1881. Krupp accurately quantified the air drag influence on bullet travel by test firing large flat-based blunt-nosed bullets. The Krupp artillery shell was 3 calibers long and had an ogival head with a 2 caliber radius. This standard Krupp projectile had a rating of 1.0, and Ingalls defined the Ballistic Coefficient of a bullet as it's ability to overcome air resistance in flight indexed to the Krupp standard reference projectile.
After World War II, the US Army's Ballistic Research Lab conducted a series of experiments at their facility in Aberdeen, MD, to re-measure the drag caused by air resistance on different bullet shapes. They discovered air drag on bullets increases substantially more just above the speed of sound than previously recognized. Further, they found that different projectile shapes had different velocity erosion due to air drag.
Fast forward to 1965: Winchester-Western published data including "G" functions for differently shaped projectiles. This included an improved Ingalls model, designated as "G1". Even though the US Army had already shown that modern bullets would not parallel the flight of the "G1" standard projectile, the "G1" drag model was adopted by the shooting industry and is still used to generate most trajectory data and B.C.'s today, for small arms use.
The "G1" standard projectile is very close to the shape of the old blunt-nosed, flat-based Krupp artillery round of 1881, which makes little sense. Every ballistic coefficient we have in common rifle use is only fractionally as efficient as the old Krupp round, and blackpowder rounds have always been among the very worst. Only air rifle pellets make them look good.
The ballistic coefficient changes with both distance and velocity. Few bullet makers acknowledge this, but Sierra Bullets is the rare exception. Here is an example: one of Sierra's .458 diameter, 300 grain bullets has a BC of .120 @ 2400 fps and above, .145 between 2400 and 1900 fps, .185 between 1900 and 1400 fps, and .210 between 1400 and 1150 fps. It is dynamic, not static, and muzzleloading rifles use a wider range of ballistic coefficients than many projectiles, as we can load the example bullet to a .145 or a .185 BC at the muzzle, and may well be using the .210 BC prior to taking our animal.
Eight-seven of my last forty-two e-mails have asked, "What is the BC of this bullet?" As you can see, there really is no answer. The only way to really know is to shoot them ourselves. I've done some testing in this regard, as has Chuck Hill. It is time consuming, and can easily destroy chronographs on a windy day, but it is the only way to really know. The best source for 100 yard muzzleloading chrono to chrono speeds remains the Lyman book, but that will always lack our exact conditions and our exact loadings, not to mention other ranges.
It is a starting point, though, and it is important. A .495 diameter round ball launched at 2000 fps can blow 18" off course with only a 20 mph cross wind, by the time it reaches 100 yards. We can certainly do better than that! Muzzleloading bullets have a relatively long time of flight compared to high velocity center fire rounds, which gives the wind more time to impart drift.
We all seek the Holy Grail of Accuracy. Make no mistake: both trajectory and ballistic coefficient influence practical accuracy. I have no excuse for ignoring them. Does anyone?
Of course, ballistic coefficients actually do exist. It is accurate muzzleloading ballistic coefficients that are not readily available. Two of the most popular in-line loads are 100 grains of Pyrodex RS pushing 240 and 300 grain pistol bullets and sabots: yielding approximately 1760 fps and 1550 fps muzzle velocities respectively.
We can expect the BC to erode with muzzle velocities higher than that, and improve with lower muzzle velocities. As the velocity decays, the ballistic coefficient rises in concert. No surprise that the bullets that are normally .44 Magnum handgun bullets come with falsely high BC's, as muzzleloading rifle velocities are higher than standard pistol velocities. The 100 grain Hodgdon Triple 7 velocities result in lower BC's, 150 grain pellet loads reduce BC to an even greater degree.
The best we can hope for is an average BC, at the velocity at which we shoot, in our specific gun. Those average BC's tend to get better as range increases, of course. For 40 yard hunting this may be a moot issue. For 200 yard shots, where BC really affects the amount of kinetic energy with which we are harvesting our game, we have much less accurate information.
Independent testing has confirmed that severely inflated muzzleloading ballistic coefficients exist, some beyond the realm of anything but fraudulent claims.
An inflated BC can get you into trouble, as you are severely misguided as to both trajectory, and terminal energy on target. A conservative BC cannot. It is not realistic to list all the "as tested" ballistic coefficients vs. the fantasy published by many bullet manufacturers. One would hope that it would be their job to "get honest," and offer some truth in advertising. That is unlikely to happen in smokepole city. Here are just a few eye-openers, though:
Actual 100 yard BC's as tested pushed by 100 grains T 7:
Copyright 2003, 2012 by Randy Wakeman. All rights reserved.