120 class powders

[Klem]

so it is possible to add power and get less velocity with poor ignition.

Have you seen this with your own eyes?

And if you have, can we repeat the test to see if we get the same results?

I agree, when you zoom in the powder/velocity curve is rarely exactly a straight line. That in some sections it appears elastic and in other sections, inelastic. That if the curve is repeatable that Satterlee encourages us to focus on the elastic sections to hone our load. But it never goes backwards. Putting more powder in never goes backwards than a lesser load. It might be an elastic increase, but never less velocity.

Another reason why the curve is never straight is Normal distribution. At each load increment there will be a range of velocities in a Normal curve. Each time you fire that load, the velocity can be anywhere on that range according to the probability represented by the shape of the distribution (as reflected by the standard deviation). The point being, in shooting we rarely get exactly the same velocity each time we pull the trigger, even if we are careful and have good equipment. We must not then see these subtle variations in velocity as indicators of precision, unless they are (1) repeatable, and (2) it actually translates into smaller group sizes.

Anyone therefore claiming to only need 10 rounds across a chronograph to figure out the best load is deluding themselves. Plus, ignoring results on target is also delusional as this is ultimately what we are trying to do - find a load that gives the smallest groups. Regardless of what velocities we're getting the barrel will be whipping around and contributing to where the bullet goes.