Newbie question:" 30 grains by volume"?


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Tallbald
April 7, 2010, 09:24 PM
"Grains" is a weight while "by volume" is just that (a volume). Now lets say that I have a powder dispenser that throws "30 grains" of black. I use the substitutes only but don't see a conversion chart of black-to-substitute. How do I handle conversions, measures or whatever? I'm sure I'm missing something simple. I just worry that a higher density substance may result in an overcharge
or a void that may get me into trouble. Please be patient with me folks. I've been a cartridge-only shooter for 45 years, and black is all new to me. Thanks, Don

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BCRider
April 7, 2010, 10:00 PM
BP is measured in volumeric grains and not weight grains. It's sort of like fluid ounces vs weight ounces. They didn't try to make this easy did they... :D

What you need is a BP powder measure to scale the volume thing. Or someone that can provide a grains volume to CC conversion.

mykeal
April 7, 2010, 11:18 PM
Bp loads are specified in terms of volumetric grains of real black powder. Substitute black powders are calibrated to meet that standard, so that, with one exception, 30 grains by volume of substitute black powder will provide very nearly identical performance as 30 grains by volume of real black powder. The one exception is 777, which gives 15% higher performance than the same volume of real black powder.

Bp powder measures are calibrated in grains by volume. The volumetric grain measure is sized such that one grain by weight of black powder equals one grain by volume of black powder. If you use real black powder and weigh your charges you can use the same weight in grains as the volume specification; that is, if the desired load is 30 grains by volume, you can use 30 grains by weight of real black powder.

The same is not true, however, for substitute black powders. You will need a weight conversion chart for the specific powder being used to determine the proper weight for a given volumetric charge.

R.Clem
April 8, 2010, 12:30 AM
mykeal is correct.
What I have used to convert substitute to weight.
Volumetric powder measure at the desired volume of powder, scoop out the desired amount and weigh about ten or so charges and get an average, then use that for weighing the charges.
It is simpler to just scoop out the amount of powder in the volumetric and dump it into a case. You won't see or feel any difference between the charges, if you don't believe it, try it.
You didn't mention what you are loading with 30 gr. of bp. If you are going into a cartridge with this, use a drop tube so the powder settles better. Then put a card wad over the powder to protect the bullet base and keep it from leading the bore. Then compress the powder to a depth that will allow the seating of the bullet without leaving any air gap. Air gaps are supposed to elevate pressures drastically, I don't know if that is true or not, just make sure there is no gap.
Bp requires a softer bullet lube, you can make your own at home from simple stuff like, beeswax, Crisco, and lanolin.
BP is a lot of fun, it is messier to clean up after, but is really an attention getter.
Triple 7 is a great product, but requires some work up. There are conversion charts on line for 777, make sure you pay attention to them.

Ray

Kruzr
April 8, 2010, 01:01 AM
Conversion for different powders:

http://www.curtrich.com/BPConversionSheet.htm

There is no such thing as a standard "volumetric grain." Grains are measures of weight. When speaking of volumetric grains, it is the volume equivalent of the weight in grains and will vary by density of the powder. For most black powders, it is close enough but it won't work for BP substitutes.

Foto Joe
April 8, 2010, 11:45 AM
I notice something missing here. It is my understanding that grains by volume is predicated on ffg black powder. Given that 3f is finer than 2f, it stands to reason that if you weigh the two, their apparent volumes will be slightly different.

Different enough to matter?? Probably not (in my opinion).

The one thing that I have learned is that volumetric measure is largely a function of exactly what you are using to measure with. Adjustable powder measure (volume) reads one thing. Flask spouts measure quite another when measured in the adjustable, up to 25% more, i.e. my 40gr spout throws 50gr in the adjustable.

I'm on the road so I don't have a scale but when I get home I'm going to find out which one is more accurate. Who knows, the adjustable might be extremely conservative and the spouts might be right on.

The issue that I have is that I only have 3f BP, will the weight/volume of 3f BP match the 2f??

Kruzr
April 8, 2010, 12:34 PM
The conversion from weight to volume is dependent upon the density of what you are converting. You can see the differences on the chart on the link of the BPconversionSheet.
Looking at the conversion sheet, there is about a 4% difference in density between FFg and FFFg of the same brand.

arcticap
April 8, 2010, 06:46 PM
There is no such thing as a standard "volumetric grain." Grains are measures of weight.

I believe that the volume of 1 grain of water has been accepted as a "sort" of standard of volume measurement for the purpose of black powder measuring devices.
The volume capacity for most every center fire cartridge case is listed as grains of water. Water is known to have a relatively standard volume for its weight which coincidentally also happens to have just about the same volume as black powder does.
And water generally doesn't have any of the density issues that black powder has either due to it's different variations.

For instance, one source lists the volume of a 9mm cartridge case as follows:

The 9x19mm Parabellum has 0.86 ml (13.3 grains H2O) cartridge case capacity.

http://en.wikipedia.org/wiki/9x19mm_Parabellum

This 13.3 grains of H2O also equals the volume of black powder that the cartridge case will hold within an acceptable fraction.
So indeed, the volume of 1 grain of water may be the standard calibration that is used by some of the manufacturers of volumetric black powder measures. Why else would any reference list the weight of water as a means of expressing the volume of a modern cartridge case?
The weight of water then must be a precise and easily verifiable way to express volume in terms of a universally known standard, that just also happens to approximately match the weight of an equal volume of black powder. :)

Kruzr
April 8, 2010, 08:31 PM
Water density is 1gm/cc and is very close to some black powders. That is how they started using volumes in the first place. The larger the variance of the density of the powder, the further "off" it will be.

Oyeboten
April 8, 2010, 09:34 PM
Hi Don,



A Powder Scale is a big help if one wishes to be particular, and definite, rather than trying to rely on conversion tables and their potential mis-haps confusions or vagueries.

So...what I have done, is to...


Measure the particular propellent in terms of it's weight in Grains for what the desired Loading is to be for that specific propellent.


See what Volume that Grain-Weight occupies...


Have or make or modify a dedicated Spout for it's dedicated Powder Flask...and, mark the Flask accordingly.


This way, changing one's Loadings from Pyrodex, BP, 777, Trailboss, or whatever, one will have everything in order and no confusions or accidental transpositions.

mykeal
April 8, 2010, 11:35 PM
Calibrating your powder measures using a powder scale is a good idea if precise powder measurements are necessary. I have 4 powder measures and they vary by 13% in the amount (by weight) of powder they throw at the same volume settings.

Tallbald
April 11, 2010, 05:09 PM
Wow this is a lot of helpful information to process. I sure appreciate all the answers, and guess I'll need to do some careful weighing, record-keeping and experimentation. I recognize the need for safe practice while doing so. Thanks so much again everyone. Don

R.Clem
April 12, 2010, 12:06 AM
A while back I got into a heated discussion on another forum about water density and volume of black powder volume. I finally went elsewhere, no sense in trying to convert someone who has been using BP all their life.
I am very glad to see someone else, arcticap, read the same article I did and understood that you can't shoot water, it is way too runny.

Ray

Carl N. Brown
April 12, 2010, 12:37 AM
Blackpowder substitutes like Pyrodex are made to be a volume-for-volume substitute for black powder.

Blackpowder charges are measured in the field with volume measures (they are not weighed in a scale).

So to use a black powder substitute like, say, Pyrodex for 30 grains of FFg black powder, you would use a volume measure set to throw a charge of 30 grains of FFg. The actual charge of Pyrodex will be lighter because it is formulated as a volume-for-volume substitute. A weighed charge of 30 grains by weight of Pyrodex would be too much. So you use a volume measure to get an equivalent charge.

R.Clem
April 13, 2010, 02:12 AM
Carl N. Brown, correct, you need to use the conversion chart in the Hodgdon manual for the conversion of BP to Pyrodex if you are going to weigh the charges. But due to the bulk of Pyrodex, they are real close when dumped into a case from a volumetric measure. Pyrodex does have some issues about compression, so I hear, I have never had any real problems.
The exception to this is Triple 7, it is all together different. You will find a different conversion for it in the manual, I recommend anyone using 777 use caution, it generates a lot more energy.

Ray

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