SD vs Accuracy

[Walt]

In the Wolfe Publishing online article that came out yesterday there was an interesting story on test-firing a Smith .45 Colt from a Ransom Rest with various loads. What I thought was most intriguing was the relationship between standard deviation and accuracy. Lowest SD is not an absolute indicator of best accuracy but it suggests that a relatively low SD, such as between about 5 and 15fps seems to do the best.

[Scott Tschirhart]

It makes sense that lower SDs would lead to better accuracy. But I am not convinced that there is a direct correlation, particularly at typical handgun ranges.

[AJMD429]

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Consistency in as many factors as possible would usually be key to hitting the same place repeatedly.

I've seen many expert reloaders try 'refuting' things like weighing powder charges, neck reaming, precision seating, and so on, and it is always interesting.

One of my most accurate loads/rifles was 6mm Remington, loaded with the 'Target' version of the little Lee Loader kit, with inside neck reamer and micrometer seating. However with IMR 4831, I could just 'dip' the cases in a cereal-bowl of powder, shake the case enough to get powder out of the neck area of the case, and finish loading the round the usual way, and still get 9 or 10 shots in a dime-sized group at 100 yards. So for that load and gun (Ruger M77V), no precision at all was needed in terms of powder charges. My thinking is that perhaps the very slow powder simply didn't completely burn while the bullet was in the barrel (there was always a big muzzle fire-ball), and 'metered' by barrel-length, the excess simply making a variation in the fire-ball.