I will probably end up feeling stupid for asking this but feeling stupid is not new to me and I am ignorant as well.
Is there an available chart or information source that lists calibers and rifling twist rates and the maximum bullet length for those calibers and twists ?  I hope I said that right so its not too confusing.  What I would like is an easy look up chart that lists those things.   For instance say I have three 40 caliber rifles        ( I wish) one with 20" twist one with 18" and one with 16" twist and I get a new 40 caliber mold that drops a bullet at 1.315" length.  I would like to have a chart to quickly check to see which of those rifles may be best suited to that new bullet.  Is there such a chart and if so how to access it ?  OK fire at will !

Wouldn't it be just as quick to punch the numbers into one of the online Greenhill calculators? That would take the velocity into account as well.

It’s kind of a rabbit hole subject, but because I have a perverse sense of humor, I’ll post this link. The numbers are based on the Greenhill formula, so if anything thing will be conservative. As in a spitzer shape will require less twist, or can be longer than the chart shows.
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I prefer a drag calculator, something you can enter a specific shape. But that makes a chart impossible. This one is one of the better free/online calculators. 

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If you look at the bullet in the calculator and compare what the chart says, you can see the difference. 

From the calculator that bullet will be fine out to 4-500 yards with a 1/20 twist. Greenhill says 1/16-17. Probably be good for a thousand yards or more.

Schuetzendave wrote on Aug 3^rd, 2023 at 6:32pm:


The disclaimer for the chart pretty much says it’s useless and why, it does tho provide a quick and easy starting point for velocities normally associated with black powder velocities, and it’s one of the few that someone took the time time try and help people out with.

A drag calculator like the one linked is what I prefer for quick and easy minimum twists. Part of that reason is it provides the twist needed from basically 500-3000 fps. Mach .5-3. The other thing that makes it handy is the use of measurements instead of calibers. Generally much easier for someone to use just starting to explore all the factors of stability. He also has a stability calculator, but it’s just the same information in graph form.
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It’ has easy access, is quick, simple and free. If you know of another something else that has those qualities, by all means post it, and I will recommend that instead.

The problem with the Miller formula is, in the words of Walt Berger and Brian Litz, is that it simply does not work for flat based bullets and to refer to their actual tested results instead of the calculator they provide for their own bullets.

If a person is interested enough to need to know the advantage that a 15 twist has over a 16 or 1.9 sg over 1.5 sg, they are probably ready and willing to invest in what’s needed to figure it out.

Sorry I can’t seem to be able to keep up with your edits.

For all the reasons listed above, is why I prefer to use a calculator that allows specific bullet inputs. JBM is a well known and trusted source. He has a quick and dirty stabilization calculator that uses the Miller formula and that calculation matches what you posted for your bullet, result is attached below. 

JBM also has a drag and twist calculator that allows bullet specific inputs. The problem is those inputs are cumbersome, such as bullet nose length listed as calibers. A .408” bullet with a .500” nose would have an input of .050”

The calculator I have referenced from Geoffrey Kolbe simplifies the same drag/twist formula by allowing measurements. 

The reason I prefer the drag calculator is that after making the inputs, a profile of the bullet is produced and you can compare to the bullet you are using, is it a reasonable match? 

Then chose bullet density, this allows for bullet construction. Cast, jacketed, monolithic whatever you shoot.

Sadly you can not include lube grooves. So the center of gravity and pressure will be off, tho not as much as assuming a boattail as the Miller formula does.

I used your, (Shuetzendave) basic bullet information, diameter, length, weight and changed inputs until the calculated inputs reasonably matched the weight. Those screen shots are also below. I am sure the bullet profile is different, without measurements, it’s a guess.  

The truth will be somewhere in between the generated numbers. But if you take the time and input the numbers of many bullets that people use successfully, you will likely find the Kolbe calculator is much closer than the Abbreviated Miller formula. It also explains why every time this subject comes up, many people chime in and say, my bullet is longer and is perfectly stable.

Basically all these online calculators use the same formula, Kolbe seems to have simply tweaked it to allow measurements by inch instead of by caliber or diameter.
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I had been promoting the Goffrey-Kolbe ballistic program for over 11 years.

I had been the best available program to solve twist rates that I could find and fit experiments that I had done, way back in the mid '80's.

Three things I like most about this program, is that it deals with the velocity range, for PB bullets (that big dip), what the CG does to stabilization and it helps to understand what happens in the trans sonic velocity range.

Here is a thread from 10.5 years ago:

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use the length of bullet that matches the gov.  500 gr.  trapdoor bullet   art

Thank you Mr. Schuetzendave but that is a wee bit over my head.
Those other charts work for me as a general guide and are simple enough that even I can use them.  Mama says simple is as simple does.