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Volume vs. weight

2K views 18 replies 10 participants last post by  jim brady 
#1 ·
I just started shooting my BP rifle and was measuring out some powder in the brass powder measure. I loaded up about 38gr and decided to see how close it actually was using my digital scale. Well the results were surprising, the digital scale said my 38gr was actually 27.5gr. So I decided just to make it an even 40gr using the brass measure and then weighed it on the digital and this time it said it was 29.7gr.

So my question is, is the brass measure that far off or is it a volume vs weight thing instead?
 
#2 ·
Grain is a unit of weight measurement, while the brass powder measure relies on volume. The weight of a charge metered by volume can vary with moisture content, chemical formulation of the powder being measured, and degree of compaction. I suspect the biggest contributor to the error you're seeing is compaction. The size and shape of the powder particles determines how closely they compact, and any tamping, tapping on the table or other forces applied to the powder measure filled with powder will alter the volume without varying the weight.

Since black powder is generally of a common density by formula, with very little variation, the shape and size of the individual particles of powder probably cause wide variations from powder to powder. From a single can of a single powder, variations have to be due to differing levels of compaction. It's possible that the measure you're using was calibrated using a different powder than you're loading, with a different particle size. Try developing a standard method of charging the measure, like filling it, then tapping it on a table one time. Then adjust the level setting to achieve the weight you want more consistently. It will always vary, as volume measurement is not consistent, and the actual charge is determined by the weight, not volume of powder, but I think with a consistent handling method you can reduce the variation from load to load a great deal.
 
#4 ·
Well, sorta. There's no such thing as a grain volume - it's a weight unit. But if the manufacturer made the measure using 4F powder as a standard for marking where the lines go, and you're loading with 2F, you're not going to get the same weight of powder as what's marked on your measure. If you shoot Pyrodex or other substitutes, the difference will only get worse.

A simple procedure will give you good, consistent loading:
1. Choose your load in grains of the powder you want to use.
2. Measure your powder with the brass measure and weigh each charge.
3. Adjust as needed to get the weight you need in grains, regardless of what's stamped on the side of your brass measure.
4. Once you consistently measure out the right weight of powder from your powder measure, write down the indicated value on your brass measure. This is the setting you'll want to use, now and always, for the powder and bullet you plan to shoot.

For instance, if your measure is set at 38 gr, but the scale says you got 27.5 gr, increase the setting of the measure until the weight delivered is 38 gr, according to the scale. Write down the setting from the measure - it might be 55 gr or so - needed to get 38 actual gr of powder. The next time you want to load this same round, refer to your notes to determine where to set your measure.
 
#6 ·
First question would be are you using real black powder or a substitute? Substitutes are lighter by volume than black and are nearly all intended to be used on a volume to volume basis, not weight.
 
#8 ·
Then you better read the directions. I expect that is a volume for volume loading. As far as I know the substitutes are all less dense than black and will weigh lighter for the same given volume. If you load by weight you might be asking for trouble.

I hope you are not, not using the black because of its age. If it has had reasonable storage it will be fine. It's shelf life with decent storage is indefinite.
 
#9 ·
Yeah. I was just at their website, and it is QUITE a bit lighter. The suggested powder charge for 38/40, 44/40 and 45 Colt cartridges (all of which normally take a 35 to 40 grain, by weight, black powder charge) is 21 grains, BY WEIGHT.

For loading loose powder (T/C Hawken, Remington 1858), it said to use volume measures.

Looks like it weighs maybe 60% of what real black does.
 
#10 ·
Just got back from the range and after shooting 8 rounds using 35gr(volume measure) I think I do not need to look any further because it shot perfectly at 40yds. Next time out I'll move the target out to 100yrds and see how she does. I know with the same charge it will reach 100yrds because on Wednesday I put a round at 100yrds and it hit about 3" right and maybe an 1" low which could have been me. I could try a lighter load just too see if I am using too much though.

I'll continue to measure my loads by volume. Thanks for all your input guys.
 
#19 · (Edited)
The thing about true blackpowder is that it isn't as consistant in chemical makeup as is smokeless powder. For that reason there may be a slightly higher content of one ingrediant than another - from batch to batch or maker to maker for the same grade of powder.

When measuring 'by volume' (for blackpowder), it is more of an excercise of averages. Because the formula used in smokless powder (by wieght) is more consistant - required to achieve various burn rates - those formulas can be measured more accurately. That is the reason why there IS a slight variance between lot-to-lot ("batch-to-batch") of the same smokeless powders produced by any given maker. That is also why people who load super performance grade ammunition pay particular attention to lot numbers on canisters and boxes.
 
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