[Unclenick]

The statistician I used to work with always claimed it took about 30 samples to have what he considered reasonable confidence the bell curve was symmetrical, though under some circumstances he would use 21. I've forgotten when? SAAMI procedures calls for 10 samples in pressure testing to prove a prospective charge for production. It seems to work most of the time, though, once in awhile an overly warm load is approved and the lot is later recalled.

We don't know how many low pressure lots get through, since they don't recall those? I'd expect them to be greater in number because most commercial makers seem to have an internal extra safety margin they toss in; particularly for older chamberings. Military ammo is loaded to within both upper and lower performance and pressure limits, though, with the result you find more surplus military ammo that's inadvertently too hot than you do commercial ammunition.

Obviously, if you fire enough rounds in load work up, that improves confidence your top load is not going to be producing unexpected extremes. I think that's what you were describing with your sets of 5? I like Dan Newberry's round robin approach for finding sweet spot loads, in part for that reason. You only fire 3 of each load level, but you've typically run through 21-30 in total and at least 9 that hover immediately around any charge that's a candidate for selection.