I`ve got a feeling the higher velocity can be attributed more to the thicker patches you used with the JBP loads. To get accurate results would require using the same patches with both powder types. Thicker patches mean the ball will be a tighter fit in the bore generating higher presure and more velocity?
Personally, I think you're absolutely spot on.
At the same time I do appreciate Hansi sharing his results...sounds likes there may indeed be an alternative to the high cost of Goex, and Swiss.
FWIW; (which ain't a lot.)
Over the years I have test shot hundreds of loads through several different chronographs while testing / developing different lubes, and I can assure you, all else being equal, the tighter patch will generate a higher velocity every time.
Now, exactly how much more pressure, and just
where that pressure peaked is another story as I have never had a way of testing any of this.
Having said that, I feel fairly confident that patch thickness alone should not be a cause for concern as I have seen, on more than just one or two occasions, folks using a mallet to start and seat a thick patched ball in hopes that they could increase pressures enough to flatten the trajectory from 100 to 200yds on the Silhouette Range.
Why is "where" the pressure peaks important?
Think of it like this:
A car can push a loaded dump truck a fairly long way, but only if he starts from a dead stop and bumper to bumper.
However, should he get a
running-go at it.....I think you get the picture.
Same thing as short-starting a patch and ball, if the pressure is allowed to build and peak before the ball reaches the end of the barrel you can well be headed for a wreck....
As long as the pressure is allowed to build as the ball passes through the bore all is well, and along with more pressure you get a higher velocity, and a flatter trajectory.
When I was a young man there was an old saying amongst the old timers of the day that "you should load 'em till they "crack"".
Meaning the sound of a "crack" was much different than the typical sound of a "Booom". the crack indicating pressure had gone up...and that holds true today. A high pressure load will sound much different than a low pressure load.
Those who loaded their rifles to this point with the powder of that time were playing with fire...literally, but 200 & 300 yard "called" shots were not that uncommon.
Sorry for ramblin.......
Uncle Russ...