Flake powder compression in straight-walled cartridges

B

black mamba

New member
In loading large straight-walled pistol cartridges like 44 magnum and 454 Casull, how much can flake powders be safely compressed? If GRT shows 105% load density with only 27 kpsi in 44 magnum, is it safe to compress it that much? How about 110% load density, could that much compression raise the pressure 7-8000 kpsi, putting it over maximum?
 
The people to answer your question are the people who make the powder(s) you are asking about.
A computer program might give you AN answer but there is no guarantee it will be a correct answer.

Talk to the makers of the specific powders, they are the only ones I would trust to give valid answers.
 
Lyman shows some pressure tested compressed loads, mostly magnums with 4227.
I would not push a computer output too far.
 
As a general rule of thumb I try to never Compress smokeless flake powders .
Load to the base of the bullet ... and maybe a slight compress ... but just to be on the safe side no hard of firm compression .
Some powders don't behave well when compressed ( Blue Dot ) so I simply don't take any chances ... no compression unless the loading manual specifies it in the load data .

I would rather be safe than sorry !
Gary
 
Here is what Hodgdon says about compressed loads:

https://hodgdonpowderco.com/reloading-education/

Normally a pistol or rifle shellcase is considered full, or 100% loading density, when the powder charge sits at the base of the bullet when the bullet is fully seated. It is possible with some powders and cartridges to increase the powder charge slightly above this point, such that when the bullet is seated it actually compresses the powder charge slightly. This condition is known as a compressed load.

Hodgdon notes in its reloading data if the subject charge is a compressed load. A full case, or lightly compressed charge is an ideal condition for creating loads with the most uniform velocities and pressures, and oftentimes, producing top accuracy.
 
Something like blue dot will fill a 9mm case and you can pretty much compress it down to normal length with the bullet on top. How much you can put in the case isn't the right question. How much you can safely put in the case is and that is determined by published charge weights.
 
This is a complex subject because you have different ignition and burn rate control strategies with different powders. Flakes, as mentioned, get compressed in shotshells all the time. The tendency is for their ignition to slow a bit with compression, as the tighter air spaces that result from the packed grains make it harder for hot gas to flow through the powder mass. However, 44 AMP's advice to contact the manufacturer is good as different flakes can have somewhat different overall burning characteristics, and what works for one may not do for another.
 
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