120 class powders

[Jimla]

One old timer told me that if you see a decrease that indicated overpressure and the velocity decrease was due to case stretching and th eprimer leaking and or backing out. That's just hearsay of course. I have never seen more powder equal less velocity but never have I seen a linear correlation either. I have been basing my load development for several years now on looking for flat spots in th epowder/velocity curve and loading to the middle of those to give myself some leeway on temperature and charge measurement accuracy. I have no idea why adding .3 gns of powder at one stage can give a 50 FPS gain velocity and the next .3 increase will only give a 5 FPS increase. But those 5FPS nodes give me the best load performance

I saw some satterlee videos testing different primers. Loads with magnum and bench rest primers had a more constant velocity curves and normal primers don't. I did similar satterlee tests myself and came up with similar results. So satterlee seems to work better with standard primers.

It is possible at different powder fill/compression ignition may differ, it is possible to add .3 gr of extra powder only for it all to exit the barrel without burning. Unburned powder is absorbing energy that could make the bullet go faster, so it is possible to add power and get less velocity with poor ignition. Best ignition seems to be 97% to 100% fill from my experience.