interesting load dev question: how do you know roughly where the nodes are?

[popeye4]

Question for Lynn:

First, I totally get your statement. Let the cartridge heat up and the temperature dependence of the powder will affect the chrono result. OK.

Now, it just occurred to me that barrel heat should have a major effect on chrono data too, yes? As the barrel heats, it's gonna expand, even a sub cal might expand enough to see a friction change in the barrel, maybe even .001" in the chamber? Enough to affect expansion volume in the chamber and friction of hte bullet moving down the bore? (affect enough to see in the chronograph that is)

Or is it cool to just start cold bore and "rapid fire" through the shots to get my data, so the first rounds are cold bore and the last are raging hot? Just so long as dwell time in the chamber is short?

How are you going to shoot? Always one shot from a cold barrel? I suppose that will give you the most reproducible data from your load, but will ignore the variability that will be present in your gun. If you are looking for one-shot optimization (which you might for a long range hunting rifle or perhaps benchrest), then letting the barrel cool between each shot might be justified. If, OTOH, you might be shooting highpower competition, there are stages where you have to do 10 shots in about a minute (even slow fire puts a round downrange every minute or so), then I'd suggest you have to test as you'd shoot. There MAY be a load that will be better in a hot barrel than a cold barrel.....