Bullet Weight Variation and Testing for Accuracy Variation

"So we probably should be arguing about how many groups are needed instead of on "blind tests" which admittedly is a refinement worth doing but much less important than shooting enough groups."

I also concur with Johns statement along with Marks explanation.  

I will add that, in the case of testing, all too often it is the size of the sample [number of shots in the test group] that really is what leads us to "self deception".  Unless 10 shot test groups are used at least at 100 yards the end result of "best accuracy" can indeed be very deceiving.  In addition to using 10 shot tests once a load shows potential the potential of that load, either in testing for terminal ballistics (group size), external ballistics (velocity, ES, SD and BC) or internal ballistics (MAP, ES, SD, pressure trace and rise) then a series of additional 10 shot tests should be conducted.  Some of us recommend at least three such additional 10 shot tests.  Only then can you have any assurance or confidence the tested load will most likely perform the same in future shooting.  

After such complete testing we must also keep in mind is testing for accuracy/group size potential the end result is not the "average" nor is it the smallest group.  The end result of the tests will be a high confidence level of the largest group of the four ten shot groups [the first test group plus the three confirmation test groups.  A higher level of confidence can be measured by using the same aiming point w/o sight adjustment and over laying the targets to get a composite 40 shot group.  

I don't see how a "blind test" could be done with such a method or using the large amount of test sample shots Litz used or what Mark suggests is needed.  The only true way to have a 100% confidence in group size, velocity, BC, SD/ES, etc. would be to shoot the entire lot of ammunition.  Thus, we are stuck with a conundrum of just how much is enough?  SAAMI says and uses 10 shot tests.  Since I began measuring internal and external ballistics 15+ years ago and began adhering to SAAMI methods I've come to believe 10 shots in a test string is enough for initial testing.

My exception is if testing a known accurate load [as in small group size] for use on a scored target.  Then I use the number of sighters and scored shots allowed in a match on the real target at the farthest distance it is to be used in a match.  In such a test I do not shoot for score nor make any sigh adjustments Other than to get on target.  What I am looking for is the groups size/cone of fire of the allotted shots for the match.  I want the cone of fire to be as small if not smaller than the 10 ring of the 200 yard CBA score target for example.  If I have a cone of fire that hold the 10 ring at 200 yards then I am confident the load will hold the 10 ring at 100 yards.  I'm sure many of us have found finding an accurate load at 50 or 100 yards does not mean it will be accurate ate 200 yards.

LMG