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On loading density: what happens when there’s more air space in the case?

On loading density: what happens when there’s more air space in the case?

I hope everyone had a good Memorial Day weekend! The weather here in Oregon was wonderful (for a change) and I made the most of the sunshine and warm temperatures. In fact, I found it hard to come back to work!

I’ve received several emails in the last few months with a common complaint: unburned powder granules lodging underneath the extractor, causing cylinder lockups. I believe the ongoing ammunition shortage may be playing a big part in the sudden increase of this problem.

Because ammunition is so hard to get, many people are either turning to reloading their own, or sliding down-market and buying reloads at the local gun show. In both cases there is a great incentive to reduce the cost of these cartridges, and one way to do so is to use a powder that requires a lower charge weight for a given velocity. Less powder used, less money spent!

As the charge weight goes down, so does the space occupied by the powder. This is referred to as ‘load density’, and is an often overlooked aspect of powder choice. In many older cartridges, like the .38 Special, .45 Colt, and .44 Special, the case volume is quite generous. Putting a small charge of powder in these enormous cases results in very low load densities.

The issue is that some powders work well at low densities, and some don’t. Hodgdon Universal Clays, which is one of my favorite powders for autoloading cartridges, doesn’t like to be loaded to low densities at all. In a standard velocity 158 grain .38 Special load, it will produce copious amounts of unburned flakes. Increasing the load density by upping the charge weight to a +P level, though, eliminates the problem.

The problems are magnified in larger cases like the .44 Special, where Universal Clays proves to be almost unusable. Just because the powder maker lists a particular load weight in a particular cartridge doesn’t mean that it works all that well!

In contrast, Alliant Red Dot handles low charge densities better, producing a clean burn at target level .38 velocities. It is now my powder of choice for low to mid velocities in the larger cases.

Oddly, all the currently available load manuals (except for Nosler’s) ignore load density. I’ve made it a policy to avoid using the very lightest powders for any given cartridge, and instead go for the powders in the middle of the charge weight range (which achieve the target velocity, of course.)

There are a couple of other factors in unburned powder issues, and I’ll get to those in a future article.

-=[ Grant ]=-

  • Posted by Grant Cunningham
  • On May 27, 2009

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