I did an interesting test with my rail gun last summer, using different powders. All tests were with the same bullet, primer, and case. All test loads were thrown on a Harrells measure, not weighed. Powders were H322 extreme, Benchmark, and S322. All were done with no change to seating depth.
Benchmark - I never got a group that didn't have some vertical in it. I went from 47 cl. to 49.3 cl. and the best was a 1/2 bullet vertical. Now if that was the best powder I would have played with seating depth from there and likely found a tune. But that was the only one close changin 1/2 clicks on the measure. If I did find a seating depth that worked it would be like balancing razor blades ( as Mike Ratigan calls it).
H322 showed the normal tune window with a second node 1 to 1/2 clicks higher.Not bad and I have used 322 long enough to be able to keep it in tune. But then I had to try the S322 that I had 8 pounds of. Started at 49 cl. and went in 1/2 click intervals to 51 cl. before I got anything that had any vertical. That means almost a full grain of powder variation is staying in tune and hitting in the same spot on the target! The cheapest scale or measure out there probably would be accurate enough to make everyone in benchrest rush out and by the latest great deal on a cheap loading tool.
Now this is a nice problem to have, but as with any great component, will eventually leave you with salty soup. (crying in your soup for you Calvin).
You hear about it all the time, someone gets a few pounds of a powder or a few hundred bullets (that are no longer made or available) and there is nothing like it. I bought this powder from a former bench shooter who gave me a deal because it was faster than the previous lot and nobody liked it. I don't even know the lot number as they bought a bunch of it in bulk and divided it up into used 8 pound jugs. I am only guessing when I say S322, but it is black and came after GI322 so is likely the Scottish made powder. I have enough of the same components to shoot one big match this year. It is locked up in a safe place and will be given a grand fairwell party in Kansas City next fall. What better place to use up a great Hodgdon powder than at a range within a few miles of where it originated? And yes Calvin as soon as the unlimited shoot at the Nationals is over all Canadians can watch me eat a bowl of very salty soup!