Traditional Muzzleloading Association
The Den - Members' Library => Resources => Topic started by: Uncle Russ on November 16, 2009, 10:25:39 PM
-
Many of us play around with our muzzleloaders using a Chronograph and Ballistic program, such as SIERRA Exterior Ballistics....the problem most often countered is the fact that many of us don't know how to mathematically compute the coefficient of a roundball, the ballistic programs are designed for modern bullets and doesn't have that kind of information built-in, so we end up knowing only the speed / velocity and are forced to make assumptions on a lot of other very valuable information.....the Chronograph and a Ballistic Program can be your friend and save you a lot of money and time if you have the right information.
By knowing the exact velocity, and the BC of any round ball, it is relatively easy for your program to compute energy, drop, and point-blank range.....out to six or eight hundred yards!
Another great feature of having this information is it will give you ES (Extreme Spread) a great way to check your loading technique and help you remain consistent with your loading procedure....as it gives you the ballistic variance of every shot fired across the screen.
I have found the following little chart, compiled from Lyman information, to be a very valuable tool with any load in my muzzleloaders.
(http://img.photobucket.com/albums/v143/RussB256/ballisticcoefficientsmuzzleloading-.jpg)
-
Russ,
How about for .610, .678, .715 and .820.
That's the sizes that I use.
Thanks,
John
-
done!
-
Russ,
How about for .610, .678, .715 and .820.
That's the sizes that I use.
Thanks,
John
John, I have always relied on a "cheat sheet" to provide me with the BC of round ball and I have never done the calculations.
However, if you own one of those calculators with scientific equations you may be able to do it....it is too complicated for me.
Here is the formula.........(Keep in mind the The French Gavre Commission decided to use a "near perfect projectile" as their first reference projectile....... The test reference had a BC of 1, and the commission named the test G1.)
Also keep in mind when reading this that the science was first based on smokeless powder and the spin-off we enjoy with Black Powder is less than two decades old.
Bullet performance
The formula for calculating the ballistic coefficient for bullets ONLY is as follows:
BC_{Bullets} = frac{SD}{i} = frac{M}{i times d^2}
where:
* BCBullets = ballistic coefficient
* SD = sectional density, SD = mass of bullet in pounds or kilograms divided by its caliber squared in inches or meters; units are lb/in2 or kg/m2.
* i = form factor, i = frac{C_{B}}{C_{G}}; (CG ~ 0.5191)
* CB = Drag coefficient of the bullet
* CG = Drag coefficient of the G1 model bullet
* M = Mass of object, lb or kg
* d = diameter of the object, in or m
This BC formula gives the ratio of ballistic efficiency compared to the standard G1 model projectile. The standard projectile originates from the "C" standard reference projectile defined by the German steel, ammunition and armaments manufacturer Krupp in 1881.[3] The G1 model standard projectile has a BC of 1.[4] The French Gavre Commission decided to use this projectile as their first reference projectile, giving the G1 name.[5][6]
A bullet with a high BC will travel farther than one with a low BC since it will retain its velocity better as it flies downrange from the muzzle, will resist the wind better, and will “shoot flatter†(see external ballistics).[7]
When hunting with a rifle, a higher BC is desirable for several reasons. A higher BC results in a flatter trajectory which in turn reduces the effect of errors in estimating the distance to the target. This is particularly important when attempting a clean hit on the vitals of a game animal. If the target animal is closer than estimated, then the bullet will hit higher than expected. Conversely, if the animal is further than estimated the bullet will hit lower than expected. Such a difference in bullet drop can often make the difference between a clean kill and a wounded animal.
This difference in trajectories becomes more critical at longer ranges. For some cartridges, the difference in two bullet designs fired from the same rifle can result in a difference between the two of over 30 cm (1 foot) at 500 meters (550 yards). The difference in impact energy can also be great because kinetic energy depends on the square of the velocity. A bullet with a high BC arrives at the target faster and with more energy than one with a low BC.
Since the higher BC bullet gets to the target faster, it is also less affected by the crosswinds.
Sorry John, but I would like nothing better than knowing the BC to two of my own guns....a .652 and a .592 (Two moulds I have had Jeff Tanner make up for me.)
Uncle Russ...
-
If I didn't have a headache when I woke up this morning, I got it now. I don't even know what some of them squiggly little marks mean - let alone how to use them. Thanks, Russ, but... I'm going back to bed now after I take about 6 Advil.
-
Looks like those equations are still in French...
-
Although such nonsense makes for great fun and gives all of us a better working knowledge of what to expect from our muskets, it is by no means a necessity in real life.
It is hard to beat the know-how one gets from actually shooting at all the ranges we can expect to encounter, and knowing, beyond a doubt, just where that ball is going to strike, at what range.
I have owned a Chronograph since sometime in the 1970's and wouldn't consider my collection of guns complete without one.
I have also owned several ballistic programs over the years and they are fun to play with and sometimes gives me quite a bit of "unexpected" information, especially when comparing actual performance to something I read in a book....it is very easy to get high velocities, flat trajectories, and exceptionally long range from a keyboard.
It is, however, a hoss of a different color to do it in real life... with a muzzleloader.
There are many "old wives tales" that simply refuse to die when it comes to muzzleloading, but a good chronograph and a ballistic program can help us see right through the smoke and mirrors....otherwise we are guessing.
Uncle Russ...
-
Ah yes, the joys of having a good chronograph. The entertainment factor alone for the folks at the range when an errant wad from a 400 grain charge in a 4 bore passes a bit low in the anticipated flight pattern and takes out your good old Chrony.
And then when you pull the trigger a bit premature on the 4 bore and the Oehler sky screens explode into hundreds of pieces - the laugh factor alone is almost worth the cost of the parts.
I have had so many enjoyment filled times with my chronographs.
-
We've all heard the saying that there are those who have dry-balled, and those who will, well it's about the same with shooting your chrono. It took me a few years, but a 44 mag does do a number on them.
-
I hate to rain on everyone's parade but, there is a big problem with BC formulas.
They are designed for bullets that are longer than than their diameter. When you plug a round ball dimensions into the formulas goes to pieces because the ratio of diameter to length is 1.000 and the formulas need to have a number less than 1.0.
If you want to try to calculate a BC or something similar dig out the old cannon ball ballistics calculators.
Personally I prefer to simply shoot since all the numbers in the world don't replace the real world.
-
Personally I prefer to simply shoot since all the numbers in the world don't replace the real world.
+1, but all the geeks will be mad at you!
-
Don't really make no difference.....as long as the ball beats the smoke there!! :hairy :applaud :wave
-
What happen to the good ol' days when we could just test how deep the ball penetrated the oak from x number of yards. :*: