Powder Grain to Volume Conversion


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jbeltz7
November 21, 2009, 12:43 PM
I'm setting up a Lee Classic Turret and AutoDisk and found Lee does not provide capicity information for Ramshot (TrueBlue) powder. The Lee chart uses a VMD factor to determine disk settings. I have TrueBlue's Bulk Density (grams/liter) 935 but have no idea how to convert this to a disk size. TIA

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rcmodel
November 21, 2009, 12:47 PM
You need to buy a set of powder scales.

I can't imagine trusting a bunch of math conversions and plastic disks with holes in them for anything as importent as what the powder charge really weighs in grains!

rc

warnerwh
November 21, 2009, 12:58 PM
A powder scale is a necessity in reloading. Without one you're asking for trouble. I agree with the above that no way I'd trust anything but a scale either. It's too easy to get excessive or dangerous pressures. If you go over max powder charge pressures will skyrocket.

Walkalong
November 21, 2009, 01:04 PM
You need to buy a set of powder scales.Plain and simple....No way around it unless you want to really limit yourself to Lees data for dippers. Even then powders vary a little from lot to lot, so you will never actually know what powder weight you are using without a scale.

06
November 21, 2009, 01:06 PM
Jbeltz, I have an extra if interested. Make me an offer I cannot refuse-LOL

jbeltz7
November 21, 2009, 01:08 PM
No debate on needing a scale, however it is a curiosity there are so many references to volume if there is not an industry standard to accurately calculate density between powders. Must be a carry-over from the blackpowder days.

lgbloader
November 21, 2009, 01:21 PM
You need to buy a set of powder scales.

Straight up... Yup.

LGB

rcmodel
November 21, 2009, 01:28 PM
however it is a curiosity there are so many references to volume if there is not an industry standard to accurately calculate density between powders. I don't know of any references to volume load data except from Lee.

Every other reloading manual in my collection only refers to powder charges in grains.

The reason is that smokeless powder is not at all uniform in volume from one lot to the next. The lot number you buy today will likely not throw the exact same weight charge by volume as the lot you buy next time.

rc

Uncle Chan
November 21, 2009, 01:39 PM
Perhaps this will help a bit.

PowderName powder CC Grains
True Blue Ramshot TrueBlue 0.3 4.4
True Blue Ramshot TrueBlue 0.5 7.3
True Blue Ramshot TrueBlue 0.7 10.2
True Blue Ramshot TrueBlue 1.0 14.6
True Blue Ramshot TrueBlue 1.3 19
True Blue Ramshot TrueBlue 1.6 23.4
True Blue Ramshot TrueBlue 1.9 27.8
True Blue Ramshot TrueBlue 2.2 32.2
True Blue Ramshot TrueBlue 2.5 36.6
True Blue Ramshot TrueBlue 2.8 41
True Blue Ramshot TrueBlue 3.1 45.3
True Blue Ramshot TrueBlue 3.4 49.7
True Blue Ramshot TrueBlue 3.7 54.1
True Blue Ramshot TrueBlue 4.0 58.5
True Blue Ramshot TrueBlue 4.3 62.9

Walkalong
November 21, 2009, 01:53 PM
Just for grins and giggles

True Blue-----07.30.04---198

Lee Dippers

0.7 CC = 10.6 Grs

1.9 CC = 30.0 Grs

3.4 CC = 52.8 Grs

Walkalong
November 21, 2009, 02:04 PM
The small differences in my weights and Uncle Chan's weights could easily be no more than how we leveled off the dippers. I just tap until it gets level. True Blue is so dense a tiny difference would show up.

Joemyxplyx
November 21, 2009, 02:07 PM
The Ramshot True Blue VMD factor is .0693 cc/gr. I don't know what you're loading, but take a .357 load as an example.

Ramshot gives a load range for a 158 Grain lead SWC bullet of 8.8 to 9.8 grains of powder. What you want to do is translate that into cc's so you want to find gr/cc. The inverse of .0693 is 14.430. Or 14.43 grains of True Blue fills one cc. So 8.8-9.8 grains fills .61 to .68 cc. The AutoDisk has hole sizes of .61 and .66 which are just about right. If you want a hole size of .68 exactly you're going to have to double disk with a micro disk. My own feeling is .61 to .66 is close enough for pistol loading.

Set up your AutoDisk for .61 or .66. Drop a few loads and weigh them to see if the VMD conversion factor is correct. As everyone else has noted if you don't weigh your setup powder drops, you deserve to blow your guns and yourself up.

If everything is set up and working, load until you're done. True Blue is a good all around pistol powder. Have fun.

Walkalong
November 21, 2009, 03:56 PM
Drop a few loads and weigh them He doesn't have a scale, remember? ;)

qajaq59
November 21, 2009, 04:44 PM
He doesn't have a scale, remember? I suspect he will by the time he gets done reading these posts. :D

Kernel
November 23, 2009, 08:58 AM
Lee's current VMD chart, dated 5-28-09:

http://www.leeprecision.com/cgi-data/instruct/VMD'S.pdf

True Blue is 0.0684 cc/gr.

The Ramshot True Blue VMD factor is .0693 cc/gr.
That's not correct, according to Lee's data. It's Ramshot Enforcer that's 0.0693 cc/gr.

jbeltz, see why you need a scale, now?

Joemyxplyx
November 24, 2009, 06:44 AM
True Blue is 0.0684 cc/gr.

Yep, that's what Lee says. Using .0684 for determining the hole size in the AutoDisk for the load range 8.8-9.8 grains gives .602 to .67cc (multiply VMD times grains for disk size).

Since the relevant AutoDisk sizes are .61 and .66, the calculated powder weight range will be 8.92 grains to 9.65 grains. The VMD factor I was using gives a weight range for .61-.66 disk holes of 8.78 grains to 9.524grains. That is a difference in maximum load of 0.13 grains. Close enough for reloading considering the max load is 9.8 grains.

All this points out the necessity of weighing the setup charges to see what you're actually throwing before reloading. As I said anyone who loads without verifying the PM setup and checking periodically during reloading is asking for trouble.

Now just for grins and giggles, take the Ramshot bulk density factor of 935 grams/liter given for True Blue. 935 grams/liter is .935 grams/cc. Converting that to grains given there are 15.43 grains in a gram gives 14.427 grains/cc. Inverting that gives 0.0693 cc/grain or a VMD of .0693 which is my original number. Curious or what?

Given Uncle Chan got 14.6 grains/cc from an actual scoop measurement, I'm inclined to suspect the .0684 VMD is probably correct and that Ramshot's bulk density factor is a little off. However, I'm still going to use a scale to check what I'm actually throwing. If I'm dancing around the max charge level, I might even use 2 scales.:)

RidgwayCO
November 24, 2009, 10:08 AM
Every lot of powder has a different VMD (within the manufacturer's accepted tolerance), and I suspect the Lee VMD charts are based on each powder's highest acceptable density.

I created a very helpful Excel worksheet that allows me to figure the actual VMD for each powder I have, and then compute the actual powder weight thrown by each Lee cavity. Of course a scale is required to initially set up the spreadsheet, and then to check that the cavity is actually throwing what's predicted.

Joemyxplyx
November 24, 2009, 12:23 PM
RidgwayCO said: I created a very helpful Excel worksheet that allows me to figure the actual VMD for each powder I have, and then compute the actual powder weight thrown by each Lee cavity.

That's a great idea. If I weren't using my LnLAP for most of my loading now, I think I'd make one of those too. I could even keep it on my Palm TX for instant reference while I'm loading. (yeah, I know I ought to keep a laptop near me while loading, but my bench top is too cluttered :)).

I could use a 1cc Lee dipper on each new powder bottle I got; throw 10 scoops onto a scale; divide by 10; take the average powder weight, which should be around 10-20 grains/cc; and put it in the spreadsheet with all the AutoDisk holes. The spreadsheet will calculate the powder weight for each hole size - grains/cc times hole size in cc's for the powder weight/hole. That would be a handy thing to have. Thanks for the idea.

fireflyfather
November 26, 2009, 01:17 AM
No debate on needing a scale, however it is a curiosity there are so many references to volume if there is not an industry standard to accurately calculate density between powders. Must be a carry-over from the blackpowder days.

There is a reason that there is no standard. As someone already pointed out, density varies by lot. It ALSO varies by humidity. So, unless your loading conditions are exactly the same as the factory/laboratory conditions (humidity, temp, or in an unlikely event how much it's been shaken around and the flakes changed size due to abrasion, or lord knows what else) you're going to end up with small variations. Hence the need for a scale.

Joemyxplyx
November 26, 2009, 09:45 AM
What fireflyfather just said - volume and density are not exactly related in gunpowders. They're also not exactly related in wheat flower either which is why bakers weigh their portions when making bread instead of just scooping out the flower.

The VMD factor is useful for figuring out about what range of hole sizes are appropriate for what you're trying to load. After using the VMD factor to pick out hole sizes, you then need to throw several loads to stabilize the powder measure and get a true powder drop. The true drops are the ones you weigh. If the drop is at the level you want, you're good to go. Otherwise you need to adjust the hole size up or down until you get the load you're after.

Using the VMD factor by itself to determine what loads to throw is just asking for trouble. A baker who just scoops flower is going to make some bad bread sometimes. A reloader who just scoops powder is going to blow something up sometimes. Always weigh the charges

RandyP
November 26, 2009, 10:47 AM
Get ye therefore a digital scale!

I own it, I use it, I like it, and for under $40 it beats using a calculator and hoping nobody printed a typo? -lol - this is just one of the many online sources, some cost even less.

http://www.midwayusa.com/viewProduct/?productNumber=785229

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