Sevens wrote:I run the same bullets at 3.6gr of Bullseye for my revolvers. I never have chrono'd that load. I found 3.4gr under the 158gr Xtreme LSWC to be very nice but lighter than I liked, and I found 3.8gr to be extremely good, but I lowered it to 3.6 and have stayed there with it.
I definitely would not change primers. I tune a load to the primer that I run, not the other way around. I know that precision rifle shooters will try different primers searching for a sweet spot, but I won't do that in handgun fodder.
Practical Application #1: Evaluating Muzzle Velocities
Standard deviation is hard to estimate with precision.
When you shoot five shots, and measure something about them, you are taking a sample.
From the sample, you hope to make some estimate of what the firearm will do in the long
run, over many shots. Since you are dealing with a sample, your estimate of the long
term performance will be imperfect, though it may be precise enough to be useful.
Suppose that a reloader is unwisely carried away with getting the standard deviation of
his handloads down to nothing. He fires five shots, and chronographs each at 2960,
3002, 2982, 2976, and 2981 fps, calculates the standard deviation, 15.04 fps, and feels
very pleased that his handloads are so consistent. But are they?
It is true enough that his sample of five has a standard deviation of 15.04, but what does
that tell us about the long-term performance of his loading technique? If we repeated this
same test 100 times, using exactly the same components and methods, then about 95
times out of that 100, we would find a standard deviation between 9.77 and 35.68.
Statistically, we say that the true, long term standard deviation could easily be anywhere
in that range. So, based on a sample of five, the shooter who thinks he has a superb
standard deviation could actually have a standard deviation as high as 35.68, which is
about typical for commercial ammunition. It was just his lucky day. The five shots he
fired happened to be very close to each other, just by luck of the draw.
The reloader that does not recognize this can easily end up chasing phantoms. One day,
he shoots test shots, and is very happy with his result. The next, things seem to have
“gone to pot”, and he can’t figure out what he is doing wrong. The fact is that nothing
has necessarily changed.
Anvil Jenkins wrote:5 rounds is not statistically valid to evaluate ES, so I would not get too wrapped around the axle about that stat based on 5 rounds .
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