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Discussion Starter #1
In reviewing powder burn rate charts, the question that came to mind is, can one compare powder pressure curves (charting) the same way burn rates can be charted?  For example, SR 7625 is a slower powder than Unique (though they are very close).  Unique's safe working pressure with a 260 gr. Keith max's at about 10 grains.  Could one extrapolate that 10 grs. of SR 7625 would provide a similar pressure curve using the same bullet??
 

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Alan,

Not really. Lists of powder burn rates that you have seen are usually compiled from a "closed bomb" test. A quantity of powder is ignited in a closed container and it's burning rate is compared to other powders.

However, this can differ greatly for a cartridge. Also a powder that exhibits a certain burning rate in one cartridge can be totally different ,faster or slower, in another. Factors like case shape, bullet weight and such cause this.

Extropolation of powder charges from one of these charts can lead to disaster depending on what cartridge you are using. The only true way to know is in a fully equipped ballistics lab with pressure measuring equipment.

Factors like burning efficiency, pressure spikes, duration of same are also measured, especially with all the new piezo equipment.

I would go by if the powder is listed for use in your particular cartridge or not.

Powders frequently change rankings on these charts depending on what cartridge they are used in also.


FWIW,


:cool:
 

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Discussion Starter #3
Thanks Contender -

Just one of the many "what if's" that float around in my head  :biggrin:
 

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Your question is similar to one I have never gotten an answer to. Powder burn rates for hand gun loads never take barrel length into consideration. There should be a difference in pressure created if a powder that is considered slow burning that works great in 4' and longer barrels is used in snub nose 1 1/2 or 2" barrels where Is it possible that the slower powders never get a chance for anything close to a complete burn and therefore never reach a desirable high pressure in the very short barrels? Would short barelled hand guns ever reach pressure maximums with slower powders or should faster burning powders be used in guns with barrels 2" or shorter to be able to build a desirable pressure in the short barrel.
 

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Search the forum on snubby loads. The problem of poor (wide extreme spread) velocity consistency from short barrels can be addressed with faster powder.
 
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