WOW 6.4 gr of Unique seems WAY WAY hot for a .38. Hell I'm using 4.9 gr. in a .38 case with 148-158 grainers and I get flack for that being hot.
But hey if it works
Have fun and be safe.
Nightshade2x
Heavier bullets usually less powder. I know, doesn't seem logical but it's physics and velocity stuff..
Try this intuitive approach and see if it helps:
Smokeless powder generates ZERO pressure if burned without containment (in the open).
Smokeless powder generates maximum pressure when completely contained in a sealed chamber with no outlet.
There you have the two limits of pressure that the powder can produce, and complete containment usually means a blown gun.
Therefore, a heavier bullet provides MORE containment and the same amount of powder would generate MORE pressure.
To keep from blowing up the gun, the allowable max powder charge is REDUCED when going to a heavier bullet.
Good explanation and better stated than mine. I understand it and was more for nightshade. By containment you are saying the heavier bullet is longer and taking up more space in the the case? Or requiring more energy or force to move the bullet out of the case due to it's weight?
How does bullet composition enter into it? Lead vs copper and neck tension of the same weight bullet. Lead usually being less powder as there is less resistance to get it moving?
I didn't really need an explanation of that, I understand the concept but thanks for your effort.
Have fun and be safe.
Nightshade2x