Gunpowder Precision
Gunpowder Precision

Gunpowder Precision

Obviously, every component of a handloaded cartridge is very important.…

Obviously, every component of a handloaded cartridge is very important. However, the only control you exercise over the bullet and primer is in your choosing what kinds to use. The cartridge case and the powder charge you can slightly modify. You can trim the case and even turn the case necks. With powder you have to settle on a charge weight, but just as importantly you need to charge each cartridge case with the same amount of powder. The only way to do this is by measuring the powder charge.

When blackpowder was the only powder shooters used, it was most often measured by volume. Due to the burning characteristics of modern smokeless powders, it should be measured by weight. However, if done carefully, it can also be measured by volume. There are basically four reliable ways to measure a powder charge for a modern cartridge. You can use a manual, balance-beam-type scale, an electric scale, a dipper scale—like the kind that come with Lee dies—or you can use a powder dispenser. All of them are capable of being highly accurate.

The Consistency Key

Regardless how you choose to measure powder charges, it is imperative that they be measured correctly and accurately. This is especially true when using fast-burning powders. Why? With faster burning powders, it takes less powder to show a change in pressure or velocity. For example, while loading a .30 Remington AR cartridge with a 110-grain Barnes Tipped Triple Shock bullet and H322 powder, I found that a powder increase of just 0.2 grain (from 40.2 grains to 40.4 grains) produced an increase in muzzle velocity of 51 fps.

That equates to a 1.7-percent change in velocity due to a 0.005-percent change in powder charge weight. Now, this might not seem like a big of a deal, but consider two things. First, 0.2 grain is a very, very small amount. Second, when you are working in the area of maximum loads, a two-percent increase in velocity and small increases in powder charge weight can very often push pressures above the established maximum for a cartridge. This is potentially dangerous to whoever is pulling the trigger.

On the other hand, an even larger variation in powder may not register a difference on your chronograph at all. For example, when using Accurate 2200 powder—which has a burn rate only slightly faster than H322’s—in combination with a 150-grain bullet to produce a .30 Remington AR load, 35.4 grains of powder produced an average velocity of 2,617 fps, while 35.2 grains of the same powder averaged 2,615 fps.

With respective standard velocity deviations of 11 and 15, these loads were, for all practical purposes, identical with regard to velocity. As for chamber pressure, we can only speculate.
So when it comes to weighing powder charges on a scale or throwing powder charges with a dispenser, consistency is very important. The question is, how can you determine or test consistency?

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