Originally Posted by
Finepoint
I think there may be a problem here in determining what is a genuinely statistically valid result. Three-shot groups are OK for determining a rough hunting zero, but for group size you need to fire at least eight three shot groups (each from a cold barrel)and average the result. Similarly, to determine velocity, you need to fire a minimum of eight shots through your chronograph and average the results. Note that eight data points are needed to be assured that the number you get is not random at a 95% confidence level. Needless to say, ten would be better, getting to a 98% confidence level.
The difference in trajectory caused by a 100FPS change is less than the random variation caused by a 1" increase in group size. Trajectory is predictable and can be compensated for; randomness can't.
Impossible to run that type of generality for statistical validity without examining the dataset itself. 10 shots out of a load with 90fps ES might not be within a 95-98% confidence interval even with 10 shots, alternatively, a load producing 10fps ES might be valid after 4 shots.
I personally have found that the 5 shot group has a lot more to do with the shooter than the rig. The odds of throwing a flyer out of a 3 shot group is relatively low, whereas it often seems that the odds of throwing a flyer in a 5shot group is almost certainty. Shoot 10 shot groups and I haven't seen the same likelihood of 2 flyers (if 1/5 is a flyer, then 2/10 should be, right? But that's just not the case). Then we have to ask the question - why are we shooting groups? Hunters don't shoot groups at deer, we throw one bullet after one target. So accuracy really is all that matters, precision is just a side effect of repeatable accuracy. (Of course, precision being the repeatability of a result, i.e. small groups, and accuracy being the ability to achieve the desired result - i.e. hit the target. Precision, in our case, is about the rifle and shooter, accuracy is simply about the POA vs. calibration of sights).
Given the right day, the right shooter, and the right rig, "groups" don't even need to be fired at the same target to produce supreme precision and accuracy (certain competitive shooting sports run this way - one shot per target).