Thread: Testing a conventional approach to load development

Originally Posted by chainsaw

Thanks @gimp for sharing your data & deductions, makes for thought provoking reading.
A couple of observations, #1 comparing the 2 20x shot pictures or patterns, the 43.6 group shows more horizontal dispersion & less vertical dispersion compared to the 44.5gn group & vice versa. At least that’s what pops out to my eyes. Both show some very good shooting skills btw. This brings me 2nd point, statistics & normal distribution….. this assumes a random error or wobble in data with a uniform set of underlying factors. I wonder if we truly have that as shooters, when the nut behind the bolt (the shooter) is as much part of the outcome as the load, pill, powder, barrel, barrel temp, fouling, etc, etc. I know my own shooting skills suffer from ups & downs. I think we’re not always dealing with a random normal distribution in load dev especially when running large numbers of shots.
Like you mention most of us started off learning load dev based on running 3 shot groups at increasing powder increments. My own learnings have lead me to run a ladder first with chosen pill & powder starting at a mid point on published data & proceeding up to book max and if no pressure signs detected then cautiously above book max until pressure signs observed, & record velocity & POI for all shots. Often the POI shift across much of the ladder is minimal, which helps establish likely sweet spot for velocity, safety & accuracy potential.

Technically I believe the distribution of radii from shots forms a Rayleigh distribution rather than normal but central limit theorem still applies.

With the approach of shooting alternately between each load, I'm confident enough that shooter error is held consistent between my 2 20rd groups shown, while it may be additive to the dispersion it will be additive in equal measure, thus the results are comparable. The point however is valid which is why I refer to the "rifle system" - this means the rifle, shooter, sight and ammunition as a unit. Any change to a part of the system may change results.

"Does shooter fatigue contribute to larger groups" is a good question to go away and test empirically, if anyone is so inclined