the "Sweet Spot"

[El Chivo]

well I'm adding to my reloading knowledge, last Sunday I fired off my first rounds of .357 using 2400. My first group was a tiny cloverleaf, and it felt just right when I shot it. That was with 10 gr of powder and a 180 gr cast.

Subsequent groups at 10.5, 11, and 11.5 started opening up or stringing noticeably. I'm getting the impression that there is one perfect load for each gun, and there's no point in going beyond that. It was probably about 1300 fps.

Is that the case, or will the groups get small again at some point?

The same thing happened with my Blue Dot load, only it happened at a lower level, 7.5 grains and maybe 1000 fps. Anything above that was inaccurate.

Is this related to pressure? I also tried a round with 5 gr of Bullseye, it had the same accuracy. It struck me that they might all hit the same peak pressure, and you will get velocity differences, with the same pressure, because of the burn rate (and amount of powder of course).

That would mean, for best accuracy, you would need a different powder for each velocity you intend to shoot at.

Is this the case, or is it more random than this? Or does it all depend on the individual gun?

[FALPhil]

I'm getting the impression that there is one perfect load for each gun, and there's no point in going beyond that.

You found the secret. For any given combination of components, there us usually one recipe that works well.

There are many factors that contribute to accuracy, but they all boil down to consistency - consistency in velocity, consistency in barrel harmonics, consistency in human factors, etc. Putting the bullet in the same hole is the result of the interior and exterior ballistics being the same from shot to shot.