I've not noticed depth changing velocity or SD's, but I've not looked for it. I don't typically make large jumps to different nodes, usually just fiddling around in the 0.030" or so where I think they should shoot. I'm a dedicated record keeper, though, so I'll go back in the data and have a look. It makes total sense that a change should affect pressure and thus velocity..
I'm just getting ready to test a load that I'm jumping 0.020" currently to the next node shorter. I'll keep an eye on what happens. The SD's on it are single digit, so I should be able to detect a change if there is one.
