http://internet.cybermesa.com/~jbm/ballistics/ballistics.html

First, what is the "perfect" bullet? It is a bullet which is three-calibers long, and ogival head of two-calibers radius, and of homogenous construction with equal and concentricity of the mass around the center from tip to butt. Got that?

This bullet must be fired from a source that will establish and guarantee that a constant velocity of that bullet will remain from the moment of launch until the moment of impact. Got that

In addition, all this MUST take place at exactly sea level, at a temperature or 59-degrees F., 29.58-inches of mercury barometric pressure and 78% humidity. Oh, and absolutely no movement of the air.

Now if we could find that "perfect" bullet, and launch it and maintain it at the "constant" velocity, under the "ideal" conditions, we would be able to assign a ballistic coefficient of 1.000 to that bullet.

All bullet manufacturers (other than Sierra) assign a B.C. rating to each and every one of their bullets under the "ideal" or "standard" conditions I have listed above. How do they derive their numbers? No, they don't travel to the moon, they do it on computers. Someone, somewhere computed how long it would take the bullet with the B.C. of "1" to travel a specified distance. For simplicity's sake, let's say it took one second. Then, they fired one of their less than ideal bullets the same distance and measured the amount of time it took that bullet to travel that distance. Let's say it took 1-1/2 seconds. That bullet would then rate a B.C. of "0.667". There are NO bullets currently available to the general shooting public that have a B.C. as high as .667! Bullets available to modern man have "rated" B.C.s of between .120 and .560. (And please remember, this value is only valid at a specific initial velocity.) Sierra saw the light a few years ago, and now assign three different "approximate" B.C.s to each of their bullets. Call them "high velocity", "standard velocity" and "low velocity". They found some bullets behaved better at lower velocities than at higher velocities...thus they have a higher B.C. at lower velocity (contrary to what many "experts" will try to tell you), and some exhibit just the opposite. And yes, some bullets perform better at medium velocities!

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http://stevespages.com/page8.htm

Last year I would have agreed with you 100%.
Now I am a believer. Their J40 308 220grain match bullet has a BC of .930. My j-36 hunting bullet has a BC of .644 and they are making me a custom bullet with the same ogive for target shooting so I can use the same drop chart for my target bullets and my hunting bullets. Ken

First of all, to compare a bullet to an airplane is comparing apples to oranges. The bullet does not fly at a constant velocity whereas the plane does.

To state that they have overcome the effects of the forces of gravity is just too bizzare. In addition they also claim to have overcome the effects of weather and atmosphere. (Granted, this could be true if the bullet was fired from the space station ... but we are here on earth.)

They specify that they have a bullet with a BC of 0.930, yet they give no details on their testing routine, nor of the velocity at which this miraculous event takes place.

Again, by definition, the "perfect bullet" must meet the specifications I mentioned above, not a list of calculated numbers (which we all know can be shimmed either way).

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quote:

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Originally posted by ricciardelli:
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First, what is the "perfect" bullet? It is a bullet which is three-calibers long, and ogival head of two-calibers radius, and of homogenous construction with equal and concentricity of the mass around the center from tip to butt. Got that?

....

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In reference to the bullet used as the "Standard" for a BC of 1.0. It's a "Standard" not a "perfect" bullet. It's placed as a "marker" with which to compare other bullets. I believe it's possible for a bullet to have a BC greater than 1.0.

Sierra has a 338 caliber 300 grain MatchKing with a published BC of .798.

Their .338 300 grainer is rated as follows:

>2300 fps=.768
1800 to 2300 fps=.760
<1800=.750

And the last time I checked Sierra is the ONLY company which specifies a velocity for a given BC, and different BC for each velocity range.

As for "standard" being compared to "perfect", a standard score in a test can be 100%, a perfect score can never be higher than 100%. And if everyone completing that test only scores 50%, that is the standard.

I do not base MY life on that sort of standard...hell, NYC just decided that a grade of 48% is passing! That is NOT acceptable to me...

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http://stevespages.com/page8.htm

You just contradicted yourself when you stated the Sierra 300-gr MK has a BC of 0.768. ???????

Not an attack, just an observation. Like King Dave stated, I too have heard of bullets (specifically for the 50 BMG) having a BC greater than 1.0. Not really sure how its possible, but I have read of such a beast. Peace

When you have 10,579 files totaling 368 megabytes of reloading data, you can't keep all the data completely updated all the time.

At the time I wrote that it was true...(Wednesday, September 22, 1999 7:29:32 AM).

Now, do you wanna piss in the wind, or do you wanna learn something?

In the past two months I have updated 2,381 files containing reloading data, and in the past year the number is 5,421...so excuse me if I didn't get to that one yet...

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So, are BCs > 1 possible? Absolutely! In fact that is typical of calibers in the 12.7 mm to 15 mm range. BC is a function of bullet mass as well as shape and as mass increases (exponentially) with diameter you get significant gains in BC. That's also why even the sleekest .224 has a lousy BC!

BC varies with velocity because of sub-sonic, trans-sonic and supersonic drag function differences. Drag force is generally proportional to the square of the velocity, but the BC will alter that figure for any discrete velocity. It is not at all strange or unexpected for some shapes to have higher BC values at lower velocities. Any shape is a compromise of features which will work best over some range of velocities and with some given degree of stabilization. At low subsonic velocities the benefit of pointed shapes is slight and increases as you get close to the sonic velocity. It is very important at supersonic velocities.

Now I take most manufacturers' BC figures with a healthy dose of salt. Barnes, in particular, is optimistic. Sierra seems to be the most honest. They, as noted, also give you some notion of how that value varies with velocity (actually it varies continuously with velocity, they just picked some mean values). You often see a lower figure from other manufacturers for more recent bullets.

A quick and dirty way to figure you BC is to chronograph your load and check the point of impact relative to the point of aim at 100 and 200 yards (make a nice group and take the center of the group). Then go look it up in a Speer manual and flip through until you find a BC that closely matches that velocity and trajectory.

Just because Lost River Ballistics' website didn't impress you doesn't mean their numbers aren't correct. The website seems to be trying to talk in a language that the average deer hunter can understand. I'll guarantee you their military customers are provided with a bit more info. I'm sure Warren Jensen would be happy to talk to you about his testing procedure.

They test their bullets at the US Army's Yuma Proving Grounds through their Weibel Doppler Radar. This gives them actual measured data on velocity, BC and drop of the bullet for every meter it travels out to way past 3000 or so depending upon the round. If that's not accurate enough, I don't know what would be. They probably just list an average over a certain velocity range for each bullet on the website.

Sierra, Nosler, Hornady, etc don't do that. Nobody else does. If there is any published BC that I'd believe it would be his.

Although I do agree that most manufacturers' published figures probably aren't good for much more than a rough starting point. Of the other manufacturers, Sierra is probably the best. When a bullet is so widely used in 1000 yd benchrest competition, if their published BC's are off one way or the other by a significant amount, shooters will let Sierra know about it (it has happened before).

I'm still wondering how Barnes comes up with such high numbers...they just don't compute!

quote:

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Originally posted by ricciardelli:
No they don't...

Their .338 300 grainer is rated as follows:

>2300 fps=.768
1800 to 2300 fps=.760
<1800=.750

And the last time I checked Sierra is the ONLY company which specifies a velocity for a given BC, and different BC for each velocity range.

....

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Sorry, you're correct about the published BC being .768. I to have too many numbers but they're stuck in my head.

When I was using the Sierra published BC I had some difficulty with the long range results (distance further than 1000 yards). The BC I personally use for the .338 cal. 300 grain is .798 which is above the published .768.

[This message has been edited by Dave King (edited 02-22-2002).]

I would not bother to put my chrony out at 100 yards and shoot at it. Unless I was "Sierra" I don't see why it needs to be that precise.

What would be a good test would be to shoot the bullets and compare them for drop, accuracy etc.

For instance a bullet may measure better but if it yaws in flight then it's real drag might be greater than a stable bullet.

Can you tell me where I might get a set of the Ingalls Charts?

I'm planning to get into the custom bullet business, and most buyers like to see a value for the BC of the bullet they are considering. If I have to I plan to shoot at my chronograph, but I'd prefer a simpler method of calculating this number.

I would appreciate any help you could give me.

Rick

Do a search for Hatchers Notebook with your computer. It may take you to http://yarchive.net/gun/hatchers_notebook.html.

I have not looked for mine yet but they are 40 years old so the source may not be the same. But check your library for Hatchers Notebook by Julian Hatcher. Many libraries had them. Also ask the U.S. Goverment printing office for Ingalls charts. This was an official US publication.

Hatchers Notebook may have the tables in them also.

All the forumlas were with those tables. It was rigorous to do some of the calculations but not to just get the B.C.

Good luck. Keep in touch.

[This message has been edited by Don Martin29 (edited 02-25-2002).]

Very small print on the envelope show this to be sold by P.O. Ackley.

I believe I bought this retail and there is no shipping data on it. The charts are copyrighted in 1936.