Question bullet velociy versus compression

[delta1]

Can anyone tell me if there is a reduction in velocity if the powder is compressed overly? Also will over compression of the powder cause more dirty residue in the barrel. Next what is the optimum compression for Goex ffg and for Goex cartridge?

[Chicken Thief]

To much pressure will deliver a hard cake of BP in a straight case, thus whats called a cigarette burn.
It burns from the ignition end through the barrel = no good!
Compressing BP gives good contact between the cernals/grains and thus good ignition. But to much is generally bad and deteriorates accuracy.

But heavily compressed BP burns much faster and gives way higher pressure, If you provide an igition channel through the charge. The powder will remain in the case and only expell gasses out the barrel, wich is way faster than a burning lumb of BP. The Danish 8x58R was loaded with a 70 grain pellet and drove a 215gr jacketed to 608m/s~2000fps in 1886.
The 303Brit was also loaded with a 70 grain BP pellet.
They pre pressed/compacted the pellet and set it in the case before neck forming!
But pressures over 2600bar~37700psi was a result of this!!!!!!!!!

[Nobade]

Yep, compress it enough and it becomes rocket fuel instead of gun powder. Last weekend I loaded some 9mm ammo with black powder to see what would happen. I could fit 11gr. in the case and compress it to just start to bulge the cases. When they were fired the boolits went about as fast as I could throw them by hand and a burning pellet of powder flew down range. Kind of entertaining but not useful for shooting. The 7gr. loads were much faster and made it to the berm!

[cajun shooter]

As with all other things in life that are good for you if used in the correct quantity so goes BP also.

[Lead pot]

I have never reached the point where the velocity stopped or flatlined from over compressing.
I have seen the increase increments diminish but never stop increasing even as much as .600"+ compression.
Here is a load work up I did for the .40-70SS from no compression to a point where I used a double compressed load.
The important thing to look at is the ES and the SD changes in the different compression ranges, and the final accuracy results for the different compression ranges from 3/4" to 3" groups.

http://i704.photobucket.com/albums/ww43/Kurtalt/40-70load.jpg

[delta1]

Has anyone found , that the more they compress the powder, the more fouling in the barrel?