1BadDart, Thanks for the compliment! Btw, I have a friend who rebuilds old cars from the chassis up. He's almost finished with a '57 Chevy that he's saved and rebuilt, including the engine (now rated at ~500 hp).
I do what the previous guys do and in addition, I weigh every bullet and keep them within .1g. I also weigh each powder charge and only go up in 3gr increments. I feel the a 5gr increment is large enough to miss a possible node where the group starts to tighten.
Yes, absolutely. 5 grn increments can hide a lot of good information. In my 40, for instance, the 5 grain step (35 grn to 40 grns) caused a jump in velocity of 230 fps but an sd of 5! This difference with only 5 grains of Goex 3F! Charges & velocities are anything but linear.
My process is to go to the range with the rifle, a selection of possible patch materials, and two different size balls.
Step one is patch testing. I shoot three shots with both ball sizes with all the patch materials at the maximum recommended charge for the rifle. Not because I intend to shoot those charges but to test the integrity of the patching. That's quite a bit of shooting and it takes a while. The patching is a marked for each shot so I know which is which. Next all the fired patches are compared and the patch/ball combination that held up the best is the patching that will be used for further shooting.
If none held up adequately then it's time to work on the bore. Don't bother shooting any more until you have cleaned up the patch cutting rifling and or crown.
From there it's just the tried and true shooting of groups with different charges until you have determined which load is best.