I constantly hear that this powder is a little faster or slower than another. Comparisons between vendors that use similar numbering schemes H4895/IMR4895 for example, indicate they're close but one's a 'little' faster/slower than another. What is a little? a lot?

Then it gets into cartridges, bullet weights, rifles, etc where it always seems that this configuration likes a powder that's, again, a bit slower or faster than BrandX.

Does anyone know of a source that explains this in boring technical detail?

Even basic things like how are the speeds measured? What is the unit of measurment? Is it something like a pressure per second measurement? If not, then what?

Given that there is some standardized method of measuring powder speed, why isn't it listed anywhere? Or is it?

I'm considering going from IMR4064 to IMR4895, Varget or VV N150. It seems that it would be beneficial to know the speed of a powder, other than just a relative comparison with another powder, during load development.

So if anyone knows where the real technical gore can be found I would really appreciate knowing how to get my hands on it.

My background is in engineering and it is very unsettling, for me, to be changing variables without knowing precisely what I'm dealing with. I know that there may be enough empirical wisdom out there to get me by...but I just gotta know!

It would help me understand another gnawing question I have about why there are so many powders and manufacturers. If there is a standardized measurement of powder speed (and maybe there isn't and therein lies the issue) then once it was determined a certain load, in a certain rifle, with a certain bullet seems to like a certain speed of powder then it would be much simpler to select a powder, regardless of manufacturer and then to use powders of known, specific characteristics while tweaking loads.

Ultimately I would like to see the powders labeled, by batch, with the speed in whatever units are used, plotted against temperature, humidity, barometric pressure, and maybe even the ignition temperature/speed (primers) etc. The temperature data would make it much easier to find powders that are less sensitive to temperature swings. Information overload? Perhaps, but...

I'm afraid my background has proven, time and again, there is no such thing as too much information. If you don't want it or need it that's great but I would like to see it available for those that do want it.

Thanks in advance and I hope someone can point me in the right direction.

Cheers,
XWind

Powder burn rate is a relative thing. The rate is usually set by the manufacture by its relationship to another of their powders. Hogdgens uses Bullseye, VV uses N110. There`s no set std to rate them with that I`m aware of. Although they are rated in some charts with respect to other brands, the rates also can change with a change in cartridge being used.

Xwind;
It would be my suggestion; to go to one of the powder manufactures web sites like Accurate Powder for example. You can pose your questions in their section called, "Ask a Tech" and one of their Lab techs will get back to you, they have been very helpful to me in the past.
Good luck,
MM

[ 02-04-2003, 07:19: Message edited by: Marsh Mule ]

xwind,

I'm a bit new at this, so I'm not going to try to tell you what little I know. The Vihtavuori reloading manual has a section that covers a bit of what you're asking and I've found an E-mail to them will get you a very quick and informative response. Good luck in your......aaaah.....quest.

Joe

XWind, your questions are from the ballistics section.
Robert (?) Rinker has written a book about all these basics and is a good entry.
The other one coming to my mind is Hatcher's Notebook. It covers a lot of topics and is imho veryvery interesting.
And the reloading books of the manufacturers:
Sierra, Lyman, Vihtavuori...

Xwind,
The way that canister powders are rated for speed is in a "ballistic bomb". A closed cell that measures pressure/time curve of a propellant when ignited in a given volume at specific temperatures. It is not likely that powder makers will publish these data or the control specifics involved in their tests. But if you do get the data I would be interested in seeing it too.

PaulS

All powders have about the same energy content. Since their "speed" is relative (a ratio) they have no dimensions. Speed refers to the slope of the pressure time curve (the first derrivative if you will). "fast" powders will have a higher peak pressure, but the same area under the curve (for a given charge). As we try to control peak pressure a larger volume of powder may be used with slow powders. This results in higher velocitu, more muzzle blast ect. (no Virginia all the powder does not burn before the bullet moves). As any case gives the lowest velocityvariation when the case is filled, considering the number of cases, the different pressure levels, the different bullet weights, and human nature, all the available powders seem to find use.

Burn speed varies lot to lot. That's a separate issue from the fact that burn rates vary according to the expansion ratio of the bore. Which is separate, yet again, from the fact that burn rate changes depending on the maximum pressure achieved.

The most useful "burn rate chart", IMHO, is the Nosler manual, which lists the powders in order of burn speed for EACH CARTRIDGE. FWIW, Dutch.