I think that if you are a short range shooter from say 100-500m then SDs are probably not going to make that much difference as long as they are reasonable. Lots of folks have shot groups that were screamers with relatively high SDs and have said there is no noticeable difference in accuracy. However in the grand scheme of things, what distance were those groups shot at and what is their idea of accuracy? I think for the Target/tactical/fclass crowd you'd probably see the top contenders trying to keep things under 12fps. Is ammo that is shooting a 12 SD going to make a difference over ammo shooting a 50 SD at 200 or 300m? My guess would most likely be no. Where you might see it would be past 500m and definitely past 800m. So I guess its all relative to what and how far you are shooting. Will a low SD help at short distances? No probably not but it certainly isn't going to hurt!
Standard Deviation for handloads
- Thread starter CoryTheCowboy
- Start date
IMHO, the bottom line is that the SD numbers, as they apply to the velocity really are not serving up any real purpose, other than (with the low data set) verify a statistical spread of the recorded velocities, which when all the variables are considered, the consequence is a fairly redundant number.
The important factor to consider in the application of the use of SD, is that the subset of the data variables remains relatively constant to be of any real meaning. For instance, when a pollster questions a population, the questions remain constant and the responses are generally predetermined to a set number. The data is then correlated accordingly.
With ammunition, there are no constants. The bullet may vary slightly in diameter, shape and weight. The casings may differ slightly in metallurgical properties, proportion and specification. The primer and powder composition is also variable in terms of weight, properties and chemical distribution.
All these slight, but inherent deviations all contribute to the overall outcome of the overall reaction once the firing pin strikes the primer.
This of course is notwithstanding outside variable influences such as the rifle itself (barrel temperature, chamber size, metallurgical properties, etc.), ambient temperature, humidity differences and the sensitivity/calibration of those factors on the measuring device itself. All this mumbo-jumbo means that the SD applied as a useful number is an exercise in futility because nothing is constant - from a mathematical standpoint.
One can use a batch of powder with one data set and have the numbers change due to opening a new bottle, couple with a casing and/or humidity change over the period of the data collection.
The important factor to consider in the application of the use of SD, is that the subset of the data variables remains relatively constant to be of any real meaning. For instance, when a pollster questions a population, the questions remain constant and the responses are generally predetermined to a set number. The data is then correlated accordingly.
With ammunition, there are no constants. The bullet may vary slightly in diameter, shape and weight. The casings may differ slightly in metallurgical properties, proportion and specification. The primer and powder composition is also variable in terms of weight, properties and chemical distribution.
All these slight, but inherent deviations all contribute to the overall outcome of the overall reaction once the firing pin strikes the primer.
This of course is notwithstanding outside variable influences such as the rifle itself (barrel temperature, chamber size, metallurgical properties, etc.), ambient temperature, humidity differences and the sensitivity/calibration of those factors on the measuring device itself. All this mumbo-jumbo means that the SD applied as a useful number is an exercise in futility because nothing is constant - from a mathematical standpoint.
One can use a batch of powder with one data set and have the numbers change due to opening a new bottle, couple with a casing and/or humidity change over the period of the data collection.
I find this is normal in the small cases like 223, even after paying the greatest attention to brass prep and powder weighing detail. I look at the groups for confirmation that I am doing things right. The ES I look at out of interest. However if the ES was greater than in the 40s I would re examine my procedures.
