Thread: Blaser R93, 30.06, keeper handload

Originally Posted by dannyb

S.D (sectional density the spread above or below your average speed for that sesssion)

Point of correction, @dannyb... SD in this context stands for Standard Deviation, and relates to how tightly clustered the velocities are around the average. A good load should in theory have a lot of rounds with very similar velocities. The odd high or low velocity round would result in a larger extreme spread but not necessarily a large SD, which is why you should look at the two bits of information side-by-side. You generally need to shoot more than three rounds though to get an accurate SD for the load.

Sectional Density is the ratio of the projectile's weight to its transverse section. Long / heavy for calibre = high SD = more penetration.

Originally Posted by mopheadrob

Point of correction, @dannyb... SD in this context stands for Standard Deviation, and relates to how tightly clustered the velocities are around the average. A good load should in theory have a lot of rounds with very similar velocities. The odd high or low velocity round would result in a larger extreme spread but not necessarily a large SD, which is why you should look at the two bits of information side-by-side. You generally need to shoot more than three rounds though to get an accurate SD for the load.

Sectional Density is the ratio of the projectile's weight to its transverse section. Long / heavy = high SD = more penetration.

quite right.....bloody Night shift I knew what i meant.....cheers for that