revolver barrel twist

[S.R.Custom]

...My quest now is for self-information. I would like to see a graph or pivot table that would plot minimum stabilization...

Let us know when you're done.

Seriously, tho, I would imagine this would be as difficult as finding a precise ballistic coeficient. What with the various bullet lengths, densities, nose profiles, etc. to consider, determining an exact optimum spin would be damn-near impossible; it's kind of tough to measure the air pressures around a particular bullet as it cuts through the air, so we really don't have any idea of what's really going on. It's pretty tough to come up with an accurate mathematical model in the general absence of data.

Greenhill's formula was hatched at a point in time where all bullets left their respective barrels at pretty much the same velocity (owing to the pressure limitations of black powder), and all bullets looked pretty much the same (round nose, 1-3 calibers long). The formula was a general mathematical guide, and at the time, worked reasonably well. Things now are a bit more complicated , no?

[jandbn]

SuperMag,

You pretty much hit the nail on the head. To say the least it is complicated and I am more than likely biting off more than I can chew. In practice, Excel works just peachy. But my head is already spinning and until it slows down, Excel won't be of much use. I don't have ballistic software that cost $ ‘cause I'm cheap. So if I'm able, I'll have to rely on my ability with math (which leaves a lot to be desired).

Maybe I haven't searched enough, but I have been unable to locate equations using RPM or twist rates plotted on an X or Y axis. So to start with if I can grasp enough to make things somewhat logical, I would "generalize" like the Greenhill type formulas. My thought for now is to "reverse engineer" (for lack of a better term) the common twist rate formulas and plot based on RPM. My fuzzy logic at this point is a boolit needs so many RPM for its length to remain stable from muzzle to impact. RPM can be calculated with the known barrel twist (with NO bullet stripping at the muzzle) and muzzle velocity. What I hope to see is a correlation on a plot line for RPM calculated on the other twist formula variables. Twist rate is based on basic variables, so maybe I can eek out an optimum bullet per RPM?

I’d start with a single cartridge, plot a graph, and then compare the results to other cartridges and "see" if anything shakes out. Also, if there is a plot line for RPM, then see if or how that correlation fits “on top” of current twist formulas. To keep “life” simple as possible, flowfield would need to be ignored. There are already enough numbers to contend with! I realize the mechanics of the flowfield are part of the total equation, but I don't really want spend time getting a "college degree" educating myself just for a hobby... unless a whole bunch of light bulbs turn on all at once. But I really, really doubt juice will flow that freely. I'd much rather be pressing a trigger than keys a keyboard!! Although… there are those cold MN winters when there's not much to do...

Ten dollars to a doughnut says what ever I end up with won’t even come close to real world experience and results!