The load density formula has provided excellent results for handloaders for many years. The main reason is simply that the load density formula works without fail. Eighty-five percent density is just about ideal, but let’s look at how reloaders have come to that number.
Density is simply the ratio of the cartridge case capacity and the actual amount of the case filled by powder. Pulling and checking some of our more accurate factory ammunition will show a density of 80 to 90 percent, so I am on the right track.
I do not like to use compressed charges. While I have done so, I cannot say the results have always been good. The reason we do not attempt 100 percent density is because there must be room for igniting flame from the primer to move across the powder charge. A compressed load would retard this action.
While I have no proof, many experienced riflemen believe a compressed charge leads to excess heat and barrel wear. By the same token, a powder charge weight that is of small density can come under what is called detonation. This is a tremendous pressure spike and should be avoided. Too much air space is the culprit of detonation, which has been known to occur even in revolver cartridges.
Calculating load density is simple, but you have to know the cartridge case capacity first. There are various methods of figuring cartridge case capacity, but many are flawed. I do not think measuring capacity by filling an empty case is relevant. I use a dummy case—with the bullet I intend to use properly seated—and weigh the case. Next, I fill the case with water through the primer pocket hole by using some type of needle or a small jet of some type. I weigh the case when filled with water, after capping the base.
Let’s say that the water capacity is 50 grains. A 40-grain powder charge would represent an 80 percent capacity of the case. Therefore, the powder charge would represent 80 percent loading density. It is seldom so cut and dry, but this is how powder capacity is measured. While this formula differs from the recommendations of those who have experience with many types of powders, in my experience it works, and it is the type of scientific notation used by factory ballisticians.
Once you have searched the loading manuals, you can narrow the choice down to several promising powders. A great boon to the aspiring handloader is the new sample pack offered by Hodgdon. This pack features small canisters of several powders and is available in a ‘varmint’ version. This is simply among the finest new products I have seen offered to experimental handloaders in some time. Again, I don’t run my handloads wide open. There are differences in performance in cold or hot weather. A load skirting on the edge just may not be completely safe in all environmental situations.
What load density formula do you find delivers the best results? Share your answer in the comment section.