VDM Tips from Titan Reloading

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VMD Explanation

The Volume Measured Density (VMD) of a powder is the volume in cc's (cubic centimeter) that one grain of powder occupies. This can be used to calculate the dipper, disk cavity or powder measure setting required to obtain a desired weight of powder.

Example:

If a powder has a VMD of .1064 , and the desired charge weight is 4 grains,

4 x .1064 = .4256, or . 43 cc's

This would translate to the .3cc dipper, (because the next larger one is beyond.43 ccs) the .43cc disk cavity, and a .43cc setting on the Perfect powder measure.

Lee attempts to keep a current list of newer powders and their VMDs on the "Instructions" page of the Lee Precision website.

Determine a VMD on your own

Using any setting on your powder measure (preferably a whole number), drop a charge of the powder you wish to determine the VMD for. Weigh the charge. Divide the measure setting you used to drop the charge by the weight of the charge. The result is the volume (cc) of a single grain of powder (VMD)

CC setting (powder measure setting)
--------------------------------------------------- = VMD (volume in cc's for 1 grain)
Weight of the sample

It is VERY IMPORTANT that you repeat this process with any new container of the same powder because the powder companies allow themselves a 16% tolerance between batches. This can result in over charging if you work from the same setting and the next container of powder you get is more dense. In any case, ALWAYS CHECK your powder drop with a scale to be sure that the desired load data grain weight is achieved.