Reloading Classics: Powder Metering
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- Last updated: 21/09/2018
Whatever method is used to measure powder charges; the critical factor is consistency. Each charge needs to be as close as possible in size to the next, otherwise the performance of your finished rounds will not be consistent. The level of consistency, or uniformity, that you can achieve depends on these main factors; powder grain shape, whether you chose weight or volume as the method of measurement, and the equipment that you use.
By far the biggest factor that influences the uniformity of powder charges measured by volume, is the shape of the grains of powder. The shape of the individual grains has a direct effect on the ‘metering’ of the powder, which is the term used to describe how consistently the powder measures. A powder that meters well, is one that can be repeatedly measured with greater precision and consistency. Ball powders consist of spherical granules that are usually small in size and they meter well, while conversely flake powders, which have granules shaped like tiny disks, do not meter as well, due to the fact that the flakes can stack-up in the powder measure. With some powders, this can cause ‘bridging’, where the powder grains stack up in such a way that they stop flowing completely and form a bridge over the outlet in the bottom of the powder hopper. When using this type of powder, you have to watch for bridging and the best way to prevent it is to give the hopper a tap after each cycle of the powder measure. Your choice of powder will normally depend more on the reloading data you use, and powder availability, but if you do have a choice of powders that you can use, take the time to investigate their comparative metering characteristics.
With no exception that I am aware of, powder manufacturers all list their loads by weight, so you might assume that reloading equipment would predominantly use weight to measure powder charges, but this is not the case. Why charges are listed by weight is the subject of some conjecture, but the most likely answer is perhaps that powder scales are very accurate, and they do not suffer from the variations that the grain shapes can generate in powder measures that rely on volume. Despite this, much of the equipment available to measure powder charges uses volume rather than weight and the reason for this is most likely the speed and convenience of the equipment that works by volume.
You can weigh out each individual charge, and this will give you the most consistent results, but if you use a balance type scale, like the superb Lee safety scale, it can take a long time. Thankfully, there are some very accurate electronic scales available now, which speed the process up, because you are not waiting for the beam to stop rocking up and down, but they are still not fast. The process of measuring by volume is generally much faster and uses tools with cavities, either fixed at a known volume, or adjustable to a required volume, which are filled with powder and then discharged into the case. Most of the measures that work this way can be attached to the press, allowing you to discharge the powder charges directly into the cases, greatly speeding up the reloading process. There are also very simple dippers, which are very small ‘scoops’, which are dipped into a tub of powder and filled with a known volume of powder.
There is a choice to be made here, between speed and accuracy, and it is up to the individual reloader to decide which way to go. The best balance, in my opinion, is to go for the speed and convenience of using a measure that works by volume, but with a LOT of regular checks of the powder charges with a scale.
With the Lee range of powder measures that use their ‘Auto Disks’, you get a set of disks, which each have six cavities is them with the capacity in cc stamped on them. They come with a table, showing the weight of most of the commonly available powders discharged from each cavity.
As the cavities are fixed, and cannot be adjusted, you only need to check the volume of your chosen powder discharged from each disk occasionally. You will soon become familiar with what cavity you use for a particular load and changing over discs is quick and easy.
With powder measures that have a single cavity, the volume of which can be adjusted, you are provided with data that allows you to work out the volume of the required powder charge. You then set the inbuilt micrometer to the volume required, weigh the amount of powder discharged a number of times and finely adjust the micrometer to ensure that you are getting the correct amount of powder discharged over and over again. This type of powder measure will have some form of locking device, to prevent the micrometer from moving out of adjustment, but the weight of the powder charge should always be rechecked each time you use it, just to be sure. If you switch to other powders, loads or calibres, you will of course have to repeat the set-up process each time.
If you choose to weigh your loads, there are many different scales available, including balance and digital types, and the level of accuracy is generally good. The Reloadr digital Scale reviewed in the June 2018 issue proved particularly accurate. The balance type is somewhat slower to use, as you have to wait for the beam to settle, but they are still very accurate. For fine tuning your powder charges, a powder trickler is a great tool. As the name suggests, these clever little devices trickle powder very slowly, almost a grain at a time, into the pan, so you can get a very exact weight.
If you have the money, there are also electronic scales that incorporate a powder feed system that discharges the powder from a hopper onto the pan on the scale, to a preset charge weight, very posh!
The choice of which method to use for measuring powder is up to you. It is a case of weighing up factors such as cost, consistency and speed, to come up with the best solution, while remembering that, as I said at the beginning of this article, consistency is the priority. Whatever method suits your budget and the amount of time you have available to reload, acquiring the powder measuring equipment that gives you the best consistency will serve you well. I will cover some of the intricacies of powder handling in future articles, and there are a number of reviews of powder handling equipment on our website that are well worth a look to help you decide what suits you best.
For Lee powder measures and the full range of Lee reloading equipment visit the Henry Krank website at www.Henrykrank.com.