Bullet drag coefficient

[Retired shooter]

Good Sat. Morning to all.

Does anyone know of a current , or at least somewhat up to date listing of all the bullet manufacturers showing a bullett drag coefficient chart.
Does such a chart exist, or do we have to research each manufacturer ourself.?

Thanks

 

[jelenko]

Here's one. http://www.shootforum.com/forum/bulletdb.html
I would be that there's one also in one of Brian Litz's books.

 

[David Milisock]

Good Sat. Morning to all.

Does anyone know of a current , or at least somewhat up to date listing of all the bullet manufacturers showing a bullett drag coefficient chart.
Does such a chart exist, or do we have to research each manufacturer ourself.?

Thanks

I only know of those by individual manufacturers.

 

[Retired shooter]

Here's one.
I would be that there's one also in one of Brian Litz's books.

Yes one in his applied ballistics book. Dont know when it was last updated.
Thanks.

 

[moondog]

Yes one in his applied ballistics book. Dont know when it was last updated.
Thanks.

Litz and crew are constantly gathering data from their mobile ballistic lab on everything that's shot through it. Applied Ballistics has data on all sorts. Not sure how to access it other than the custom curve in a Kestrel.

 

[dcali]

There isn’t any public source of the drag coefficients that I’m aware of. The best you’ll do is use something like McDrag and measure all the bullets. It’s a huge pain.

 

[jelenko]

Sorry. In my post above I forgot to include the link to a database of bullets that apparently comes from QL
I've edited my post above to include the link and here it is again http://www.shootforum.com/forum/bulletdb.html

 

[Retired shooter]

Since quick load has been mentioned, what is the general consensus on it.?

 

[dcali]

Since quick load has been mentioned, what is the general consensus on it.?

It’s very good in my experience. But the software is written like it’s 1990. It’s in bad need of modernizing. They’re just burning money by not doing that if you ask me.

 

[Retired shooter]

Thanks

 

[CharlieNC]

It’s very good in my experience. But the software is written like it’s 1990. It’s in bad need of modernizing. They’re just burning money by not doing that if you ask me.

Gordon Reloader Tool is free and has more features as well.

 

[mikecr]

The QL bullet tables, and Litz books do not list drag coefficients per mach#.
They're just showing some random BCs for different bullets.
Also, I seriously doubt many bullet makers would spend so much for that kind of testing, since that info in itself does nothing for customers. Maybe Berger did in development of their hybrid designs.

The only drag coefficient tables I've seen (and have) came from Aberdeen BRL.

​

 

[RegionRat]

Go to the trajectory calculator, find the drop down menu for the bullet and search to see if the one you like is listed. A whole library of bullet ballistics stats is gathered under that drop down menu that represents many sources.

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Bullet Library​

The JBM Bullet Library has approximately 2000 bullets from as many manufacturers and sources available. They are arranged by Manufacturer, Caliber (in inches), Weight (in grains) and Description. Bullets are listed in the same way the manufacturer lists them which leads to many different descriptions (e.g. BT, Boattail, SP, Soft Point, etc) but this allows one to find the bullet from the manufacturers data.

It is important to remember that the output of the calculator is only as good as the inputs and one of the key inputs is the drag data. Most of the data comes from manufacturers websites (see BC Links) and consists of the typical G1 ballistic coefficient. These values are either measured or estimated and I believe represent the company's best effort to find the BC.

When other sources of data are made available they are input into the library. These sources have a short indication of the source of data in the description. The two most common are the Lapua CD data and Bryan Litz.

Bryan Litz, the ballistician for Berger Bullets has recently published his book on long range ballistics, Applied Ballistics for Long Range Shooting. This book, among other things, includes software and experimentally measured ballistic coefficients for 175 bullets. The bullets have been added to the JBM Bullet Library using the G7 drag function bullets measured by Bryan are denoted by "(Litz)" in the description. The G7 coefficients should give better calculations than the G1 coefficients over the ranges typically fired in long range shooting. When given the choice of the manufacturer's data or the measured coefficients, I would try Bryan's data.

Lapua has released CD (drag coefficient) as a function of mach number for some of their bullets. This data typically contains over thirty coefficients to model the drag of the bullet. The data for these bullets can be found here toward the bottom of the page. The Lapua bullets in the library that use the CD data have "(CD)" in the description.

 

[dcali]

The QL bullet tables, and Litz books do not list drag coefficients per mach#.
They're just showing some random BCs for different bullets.
Also, I seriously doubt many bullet makers would spend so much for that kind of testing, since that info in itself does nothing for customers. Maybe Berger did in development of their hybrid designs.

The only drag coefficient tables I've seen (and have) came from Aberdeen BRL.

​

I do (easy for me with only two bullets) and Lapua does as well. I don’t think anyone else does. If there were an open standard for drag functions that all the calculators used, you might see more of that. I know AB tests bullets, but they hide the drag functions behind their calculator. Hornady does the same thing if memory serves. I would like to see more companies follow Lapua's lead and just release the tables. There's no magic secret sauce in ballistics - I can assure you that any of the major manufacturers have the knowledge and capability to produce bullets to whatever BC/caliber/length parameters they want, so I'm not sure why all the secrecy.

Interestingly, you'll see a pattern when looking at real bullet drag functions - the real drag function looks a lot like the G7, except at transonic velocities. In that region the real function tends to be about half way between the G1 and G7 standards. In other words, you could make a drag function that would be more accurate than the G7 *and use a G7 BC* for the bullets we use. It's not even hard - you just tweak the curve a little bit. I thought about building this into my calculator, and may at some point do that. But ultimately it really doesn't matter. At sane ranges, the G7 is plenty accurate. And at ELR, you might as well go for the full proper drag function. But it's interesting that there appears to be a "missing" standard that's better than G1 or G7.

 

[243Mendoza]

From Vaughn:
BC=0.00007143*W/(D^2*Cd)*sigma
where W=bullet weight in grains
D=caliber in inches
sigma=density factor

(but Cd is also a function of Mach Number which may be important in long range shooting)

 

[FeMan]

Remember....altitude, temp, humidity, speed, etc will change B.C.

I concur that speed affects BC. The others listed certainly affect air density which in turn affects bullet flight. If you mean they actually change the BC, can you explain?

 

[Doom]

Just for clarification the following is from Hornady and Berger sites. You are left somewhat to your imagination as to the interpretation of the values. Are they single point or average to velocity. I interpret the these as single point values and I would ignore the 2.25 value in most cases and use the 2.0 value until my velocity drops below 1950 fps then use the 1.75 number.

Hornady:

• "Mach 2.25 (2512 fps* and above) - Velocities above 2,500 fps and distances out to 300 yards.
• Mach 2.0 (2232 fps*) - Mid-range shooting where the bullet spends time in flight after slowing down.
• Mach 1.75 (1953 fps*) - Long-range shooting where much of the bullet flight occurs after velocity loss."

Below is from Berger's No BS BC.

"Berger Bullets is committed to the success of our customers, which is why we publish BCs which are measured from live fire doppler radar testing, and averaged from 3000 to 1500 fps".

Sierra has stayed with G1 but usually provides three values to be used with velocity ranges over which the value appears to be an average for the range.

 

[dcali]

What nobody will say out loud is that BCs are subjective. When presented with a measured drag curve, you have a fair amount of leeway in choosing a BC that best fits that curve.

If you’re getting to a point where you care about subtleties of BCs, you probably shouldn’t be using them.

 

[RegionRat]

If you don't have a chance to shoot with a capable radar, you can work around the problem by using drop data at several distances along with the velocity from ShotMarker at the target. Once this is coordinated with climate data at one or two altitudes, you can bound the BC fairly well for down to say M1.1

You just have to remember there are changes to a barrel and what it does to a bullet from BOL to EOL, so capturing data at every opportunity would need to become a habit if DOPE predictions are important.

 

[Laurie]

But ultimately it really doesn't matter. At sane ranges, the G7 is plenty accurate. And at ELR, you might as well go for the full proper drag function.

That probably sums the situation up for most competitive shooters. As a known-distance out to 1,200 yards (but far more commonly 1,000 maximum) prone shooter allowed 'sighters', I've never felt disadvantaged by using average G7s. Using 308 Win and 223 Rem at 1,000 in the days of G1 values, unreliable chronographs, and by today's standards high-drag bullets, was a very different matter and you just hoped you'd chosen a bullet that retained its stability through trans and sub-sonic boundaries.