Jordan Smith has exactly correctly described the difference between sample and population.
Also, standard deviation is a biased estimator, not an unbiased one. On average, it will underestimate dispersion, particularly with small samples. Variance and range are unbiased.
The uncertainty in any estimate of variation with as few as 5 samples is surprisingly large. SD is a lot harder to pin down than averages are.
It depends on what you determine to be your confidence interval value. Is a 95% confidence interval apply to velocity calculations? I took several classes in statistics and modeling in college, but I never gave much thought to how they apply to shooting statistics, for some reason.
