What seems apparent is that internal ballistics and pressure curves are rigorously complex and that powder mfgs are not providing sufficient technical data about their products.

Insofar as these products are potentially life threatening, it seems reasonable to argue for full disclosure rather than buying the industry's argument that such disclosure may provide handloaders with data that may prove dangerous.

Some of us are mechanical and chemical engineers. (NOT me!) Lacking the sophisticated equipment necessary to derive the data ourselves, such data should be provided the consumer if for no other reason than to illustrate what a complex equation internal ballistics can provide.

Currently available velocity/pressure data provide little more than a limited number set of coordinates situated on the slope of a powder's performance curve.

Powder performance curves are NOT a straight-line slope and possess such statistical complexities as a pressure "toe" and a "spike." From what I can garner with published data, even the "load window" in the slope contains complex variables.

It is absurd to hope that we might be able to monitor such complexities through the primitive data gathering methods of case expansion, primer flattening, sticky extraction, etc.

It's time the mfgs stopped limiting us to "a shot in the dark" with respect to load characteristics and powder performance.

[This message has been edited by Genghis (edited 01-14-2002).]

All the stats I've been able to dig up say that the old CUP system had a large amount of random error, even after you average 10 rounds. As I've said before, the fact that most of us still have both eyes and all our fingers is more a credit to conservative firearm design that to the old measurement system for establishing maximum loads. It seems entirely possible that the manufacturers don't have a very clear picture of some of the pressures their stuff produces.

There is no reason that a careful reloader, with a few hundred bucks worth of the right electronics, cannot produce pressure data of adquate accuracy and precision.

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Originally posted by denton:

There is no reason that a careful reloader, with a few hundred bucks worth of the right electronics, cannot produce pressure data of adequate accuracy and precision.[/B]

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Well . . . begging to differ here. In order to get a complete data set on internal ballistic performance you need to collect data on upper end pressures. It's the upper end pressures and the curve they exhibit that allows you to "plot" pressure characteristics.

Somewhere past that "maximum" charge weight, there's a spike where pressure rapidly increases. The characteristic of smokeless powder is that it generates pressures by igniting under pressure. At some points on this pressure slope ignition is predictable and controlled. Beyond this "load window" the slope spikes and ignition/pressure becomes volatile.

Pretty difficult to find where this slope/spike lies without loading significantly/dangerously past maximum charge weight data. Loading past SAAMI spec requires specialized (expensive) equipment.

Too bad we can't draw graphs in this forum to illustrate our points.

X axis represents pressure and runs up and down the side of the chart.

Y axix represents load weight and runs horizontally across the chart.

Angle of the "toe" is fairly flat -- let's say 10 degrees.

Angle of the "slope" is steeper but at a constant angle -- let's say 30 degrees.

The "spike" is the point at which small increases in load weight result in large increases in pressure. Let's say for the purposes of illustration that the spike rises at an angle of 70 - 80 degrees.

Nitro cellulose and nitro glycerine (bases in smokeless powder) generate pressure by igniting under pressure. The more pressure they encounter, the more pressure they generate. This is why smokeless which is not contained produces little more than a flash of flame. Smokeless powder under pressure generates pressure. Increased pressured drive the pressure curve steeper and steeper -- into a "spike."

Optimal internal ballistics distributes pressure across an even slope. Artillery ballistics stive to sustain an even pressure slope and to avoid a pressure spike in the internal combustion of the charge.

Very fast powders can produce a steep spike and then "toe out" as the bullet travels down the barrel. BUT, this is because ALL the powder is consumed in the spike. IF sufficient powder remained to be burned, the pressure spike would continue to climb, quite possibly at an increasingly steeper slope.

US Marine Corps Artillery Manual is online and discusses this concept. No, I don't have the link.