Load development I use:
In physics, there is no free lunch. In closed thermodynamics systems such as the internal ballistic solution, the goal is to get:
1) A very low MV SD vs powder charge load
2) Small groups vs powder charge load
3) MV velocity stability vs powder temperature
4) MV velocity stability vs small powder variations
5) MV velocity stability vs primer choice
6) Low vertical dispersion at very long and extremely long ranges vs bullet selection
First, let us solve the issues related to goals that we can control pretty easily. More specifically, 3) 4) 5) and 6)
3) Use temperature stable powder such as IMR endurance, Hodgdon Extreme Powder, etc. There are many online tests that you can search for and find what powders are the most temperature stable (e.g., H4350)
4) Measure each powder drop to less than 0.1gr accuracy. It is easy to get to 0.02gr (1 extruded kernel) which is worth 0.3fps out of typical load
5) Make a small ladder test and see if the selected primers would produce a smoothly rising curve, if not, do not use those primers.
6) Use VLD bullets with very low variations in G7 BC. For example, pick VLD bullets with less than 1% variation in G7 BC. Now, here we finished the goals that are virtually 100% influenced by the components
Now, let us focus on the loading for the node. What is the node after all?
Optimum Barrel Time, OBT node: It is the node (with respect to time) where the bullet leaves the barrel when the muzzle is subjected to the least dilation/contraction due to the powder explosion shock waves
Optimum Charge Weight, OCW node: it is the node (with respect to time) where the bullet leaves the barrel when the muzzle is pointing to the same point of impact due to the powder explosion shock waves
Optimum Feet per sec, OFPS node: it is the node (with respect to time) where the bullet leaves the barrel with the minimum SD of MV due to the powder explosion shock waves keeping all parameters the same, changing the powder charge can change the MV and inversely the actual barrel time of the bullet
Note: OFPS is my theory why MV SD would shrink for the same powder but by just changing the powder charge. What node are we after?
Goal 1) is solved with OFPS node, a theory I introduced in September 2018.
Goal 2) is solved with OBT time. The good news, OBT is numerically computed. With the advancement of very accurate radar-based chronographs and internal ballistic solvers, the OBT charge load can be accurately calculated. I had success doing that for a few competitive shooters as proof of concept.
How about Goal 1) the best way to find it in my experience is to shoot a group of 3-5 shots in a ladder test such as the 6.5group spreadsheet test and find the lowest MV SD The bad news is OBT node (the smallest group) and OFPS node (the lowest MV SD) don't overlap. Remember, in Physics, there is no free lunch. The good news is both nodes are adjacent and in my experience, if you find the OBT node, the OFPS node is the next step load in the ladder. As groups shrink, MV SD will increase and vice versa. So, the best is to find a compromise load between OBT/OFPS nodes that works for the shooter.