Charging Cases for Best Accuracy:


Explanation of How to Charge Cases for Best Accuracy
(rev. 8/03)

The following text is a report on the method I use to obtain very precise filling of the ctg. case and explains why it is a vital requirement when trying to make match grade black powder ammunition.

By Dick Trenk, Competition Events Coordinator, Davide Pedersoli & Co.

There is always confusion with regards to what type of "grains" we are talking about and this clarification has been posted many times in past years. Read and remember what is written here and when you later read or write about charge weights, make certain the grains are properly identified as mentioned below.

Because most BPCR shooters reload for several different bullets, they will also develop accuracy loads which use different "volumes" or "weights" of black powder.

For this reason we want to start out by using what is called an "adjustable powder measure." This device is used by almost all muzzle loading shooters and is available from all shops catering to black powder, muzzle loading or shooters supplies.

The advantage of this device lies in the fact that the load volume can be changed in small amounts according to the markings and the device can be accurately returned to any volume number desired.

This "adjustable powder measure" is a simple brass tube with a sliding piston inside. The piston rod is marked with numbers representing the "volume" of grains at which the piston is then set for.

1) Scale weight grains are NOT the same as the volume grains we use with the hand held adjustable powder measure used by muzzle loaders.

That sliding piston device is marked in grains of WATER, which is of course a liquid measure grain, which does not agree with a dry measure grain (avoirdupois) having 7000gr. per pound, which is what your powder scale is using.

2) Because of this big difference between scale wt. and the volume wt., the volume grain wt. will be much smaller than when that same charge is weighed on a scale. In other words, the charge volume grains you use will have a much higher grain wt. on your scale.

Example: Volume of 62.0 gr Swiss 1.5 Fg will weigh on my electronic scale 72.7 gr.
This is for a "settled" charge in the adjustable measure.

I suspect that when original black powder cartridge powder capacities were printed, they actually referred to the "liquid volume grains" because black powder was in olden times dipped from kegs or poured from powder flasks. Reloaders before the advent of metallic cartridges didn't own precision scales based on the avoirdupois weight system of 7000 grains per pound, as we use today for smokeless powder measurements.


Thus an original 45-70-500 ctg. was charged with a fast dipped or thrown, 70 grains volume of powder, which became highly compressed when the bullet was seated and the crimp applied to the case.

A common unit of measure for black powder was the DRAM from the liquid dram used to measure alcoholic beverages. This is the origin of the so-called "Dram Shop" laws made to control saloons and bars nationwide. Today this term DRAM is still used in reference to shotgun shell reloading and is a carryover from those bygone days when both shot shell as well as rifle and pistol cartridges were filled according to the volume of water (liquid) grains they would use.

3) Because of this serious difference, it has been requested that writers always state if they are referring to scale grains or volume grains of black powder. If this simple clarification is not provided, the reader could be way off when attempting to copy powder charge data.

We don't have this problem in talking about smokeless powder because the scale weight system is always used, not the volume method.

4) Because powder compression affects BP accuracy much more than does a slight charge weight variation, it becomes more important to have a charge in the case settled to a constant height, before actual mechanical compression takes place.

This is only obtained when a volume method is employed because the volume method will give you (more closely) the same powder column height each time but the scale weight method will not produce as closely, the same powder column height each time.

The reason this happens is simply due to the irregular shapes of BP grains and also because of the large tolerance allowed in screening the various "F" system grain sizes.

5) Black powder is an inefficient burning powder compared to smokeless powder. This means that we can have quite a bit of powder "weight" variation between each cartridge and find they all shoot about the same speed and accuracy. Therefore, scale weighing each charge does not tend to produce more accurate ammunition.

However..... BP burning rate is strongly affected by the amount of compression applied to it. Variations in powder compression is easily seen on the chronograph as well as on the target paper.

But.......in order to obtain even and consistent powder compression, we MUST start with even and consistent powder column heights in the ctg. case.

6) After many, many tests under well controlled conditions I have personally satisfied myself that ammo carefully made with the "volume" method does produce lower SD (Std deviation) and ES (Extreme Spread) than when the same load is made with scale weight methods.


However, there are plenty of winning shooters who will disagree with what you just read and they get accurate ammo by weighing each charge of BP.

7) The dipper or Lee type dip cup does a fairly good job for hunting and plinking loads but won't produce match grade accuracy because there is no consistent "settling" involved.

To obtain consistent accurate volume in an adjustable measure or from some other powder dispensing device working in a similar manner, the operator must fill the device over the skimmer line and while a reasonable "head height of powder" is maintained over the top of the device (skimmer line) the device must be vibrated or knocked in a repeatable manner so each refilling will settle the same amount of powder into the device before the skimmer or drag plate is used to skim off the excess overfilled powder.

I do this in a simple manner by holding the adjustable measure over a large glass bowl, which catches spilled powder. A small powder funnel is held against the top of the measure and a quantity of powder spooned into the funnel, which will FILL the adjustable measure and leave about 1.0 inch of powder height in the funnel. The joined measure and funnel are kept together and tapped on the bench 12 times (in a consistent manner) to settle the powder into the measure.

The funnel is then slowly dragged off the measure and excess powder falls into the bowl and later reused.

What this has done is to fill the measure with a repeatable settled volume of powder.

This charge is then poured into the case via a drop tube or as I am currently doing, dumped into the case fast and the cases are vibrated on a home made (electric razor) device for 25 seconds.

The vibration device consists of a tin cookie box with open ends and large enough to allow a wood loading tray with 50 ctgs. to sit on it easily. The old electric razor is epoxied into the tin box and gives a perfect mild vibration , not too strong so as to throw powder around inside the brass cases, yet strong enough to promote nice even grain settling. You can make a similar vibration box using any sort of device, which produces "mild" vibrations.

I found that the final powder height in the 25 second vibrated cases exactly equaled that obtained via the 32 inch drop tube and since this fast dump method is quicker than the use of the drop tube and results in the same accurate "final" powder column height, this produces the needed accuracy and saves lots of bench time as well when you do it for a block of 50 cases at a time.

Ammo accuracy and muzzle velocity and ES is exactly equal on both types of charging methods (vibration or drop tube).

The black powder seems to be dumb...and cannot tell if it fell down a drop tube or was mildly vibrated to it's final column height!

The ES using any powder lot of the Swiss powder is single digit and is usually 5-7 fps and at times I have fired 10 shots with an ES of 2 fps.

Low ES can be obtained with Goex (2002 and later,) or with Elephant (Lot 25/99 or later) powders. Due to the inconsistency found in other lots made at other times and with other brands, you may have difficulty getting the low ES figure from such powders.

One of these days I will get one of those handsome Pedersoli MoA Challenge plaques if my eyes don't fail me.

Now, as we enter the 2003 shooting season, I remind you all again that Pedersoli offers nice Italian Holiday trips, free rifles, and other awards for winning a State, Regional or National match.

Details are seen on http://www.davidepedersoli.com along with "Minute of Angle Challenge" rules, and also how to join the Pedersoli Shooters Assn. for free!

Dick Trenk
Competition Events Coordinator
Davide Pedersoli & Co.