weighing powder, just wondering

[wiiawiwb]

I'll reload 30-50 rounds at a time. Sometimes, if I am really in the mood 80-90 rounds. Each one has powder scooped and measured on a scale. Each round is examined after seating and then again after crimping.

Probably stupidly obsessive but I actually enjoy taking my time with it.

 

[Unclenick]

Since powder is measured universally by WEIGHT…

Check out Lee's VMD charts for their powder measures which are calibrated in cc's.

....how would one KNOW if "thrown charges" are in fact "more accurate" than weighed charges ?

You adjust your powder measure to dispense an established accuracy load (whether established by weight or by volume originally) and dispense powder for one sample of cartridges with it and dispense a second sample the same size by weight. Shoot each sample into one giant group on a target, alternating between targets and samples with each shot so that barrel fouling and heating and the effect of any mid group barrel cleaning you do is equally shared by each sample. Then compare the sizes of the groups.

No one measures powder based directly on volume - "I use 1.27 cubic centimetres for that bench rest load in my .308" - or something like that.

Lee does exactly that.

Charges dispensed by volume ALWAYS correspond to a target WEIGHT.

Only if that's how you worked the load up. Ask any black powder shooter if they've ever weighed a charge. There is absolutely nothing stopping you from determining about how much to adjust your powder measure to get a third to half a grain more powder, checking it by weight only at the starting load, then doing your workup only by adjusting the measure in that increment at each step toward maximum. You then watch for pressure signs, same as anyone else.

So, if your powder thrower dispenses a bit more (or less) than the target - then it simply dispenses inaccurately - at least with that particular powder. How is that desirable?

It's not desirable if your powder has an exactly stable moisture content and never responds to packing with a change in burn rate. It is desirable if the reason your charge weight is varying is because the moisture content is changing, because then volume comes closer to dispensing the same amount of chemical energy each time than equal weight does. It can be desirable if, after weighing, you don't control how uniformly the powder packs into the case.

As long as the scale used to weigh the charges is accurate, then there is NO difference.

Except possibley for moisture content and packing.

Sorry, but the idea that thrown charges are somehow "more accurate" than weighed charges is nonsense. Either the charge WEIGHT is correct - that is, equals the DESIRED weight - or it doesn't. How you get there doesn't matter, except in the sense of how much time and effort it might require.

Try reading my long post again. It's already explained. Look for past posts by Bart B., a former U.S. Palma team member, describing the very thing you refuse believe is possible. It happens. Not with all powder and bullet and cartridge combinations, but it happens pretty regularly. You'll just have to try it to see if it's true in any of your guns. Hang the theorizing; the proof is in the pudding.

 

[kilimanjaro]

You cannot be too anal about checking the weight of your powder charge.

I check the first batch, then intermittently, then the final handful, for charge. When I'm done, I weigh each and every round singly, any discrepancies beyond a few grains get disassembled and reused.

 

[wpsdlrg]

Quote:
Originally Posted by wpsdirg
Since powder is measured universally by WEIGHT…
Check out Lee's VMD charts for their powder measures which are calibrated in cc's.


Quote:
....how would one KNOW if "thrown charges" are in fact "more accurate" than weighed charges ?
You adjust your powder measure to dispense an established accuracy load (whether established by weight or by volume originally) and dispense powder for one sample of cartridges with it and dispense a second sample the same size by weight. Shoot each sample into one giant group on a target, alternating between targets and samples with each shot so that barrel fouling and heating and the effect of any mid group barrel cleaning you do is equally shared by each sample. Then compare the sizes of the groups.


Quote:
No one measures powder based directly on volume - "I use 1.27 cubic centimetres for that bench rest load in my .308" - or something like that.
Lee does exactly that.


Quote:
Charges dispensed by volume ALWAYS correspond to a target WEIGHT.
Only if that's how you worked the load up. Ask any black powder shooter if they've ever weighed a charge. There is absolutely nothing stopping you from determining about how much to adjust your powder measure to get a third to half a grain more powder, checking it by weight only at the starting load, then doing your workup only by adjusting the measure in that increment at each step toward maximum. You then watch for pressure signs, same as anyone else.


Quote:
So, if your powder thrower dispenses a bit more (or less) than the target - then it simply dispenses inaccurately - at least with that particular powder. How is that desirable?
It's not desirable if your powder has an exactly stable moisture content and never responds to packing with a change in burn rate. It is desirable if the reason your charge weight is varying is because the moisture content is changing, because then volume comes closer to dispensing the same amount of chemical energy each time than equal weight does. It can be desirable if, after weighing, you don't control how uniformly the powder packs into the case.


Quote:
As long as the scale used to weigh the charges is accurate, then there is NO difference.
Except possibley for moisture content and packing.


Quote:
Sorry, but the idea that thrown charges are somehow "more accurate" than weighed charges is nonsense. Either the charge WEIGHT is correct - that is, equals the DESIRED weight - or it doesn't. How you get there doesn't matter, except in the sense of how much time and effort it might require.
Try reading my long post again. It's already explained. Look for past posts by Bart B., a former U.S. Palma team member, describing the very thing you refuse believe is possible. It happens. Not with all powder and bullet and cartridge combinations, but it happens pretty regularly. You'll just have to try it to see if it's true in any of your guns. Hang the theorizing; the proof is in the pudding.
__________________



Hairsplitting. Plain and simple.


Yes, Lee sells dippers that are calibrated by volume. That volume, however IS predicated on a certain WEIGHT. Volume is merely an indirect method to arrive at a certain weight, nothing more. I will not even address the inherent "baloney" (to use a benign term) inherent in insisting that powder dippers, or for that matter, volumetric powder dispensers, will somehow produce more precise or "accurate" loads, vs. weighing powder charges on an accurate scale. Two methods designed to arrive at the SAME result.

I'll put it another way. If one determines through testing that a charge wt. of XX, in a particular cartridge, provides the best accuracy for that cartridge in a particular firearm.....whether that charge is measured by weight or by volume, DOES NOT MATTER. The best charge is the best charge - it will weigh XX....and the volume will correspond directly, for the particular powder in question, to that weight. How is that difficult to understand ?

If you want to try to obscure the issue by bringing in extraneous details such as "moisture content"....which has nothing to do with the method used to measure the powder....so what ? Two samples, taken from the same container, will have essentially the SAME moisture content. Therefore, moisture content is meaningless for purposes of this comparison, excepting that it COULD introduce inaccuracy in charges measured by VOLUME.

As for "packing", that is an issue which can introduce errors (or inaccuracy, put another way) in charges dispensed by VOLUMETRIC means. It has no bearing on WEIGHED charges. It actually serves to mitigate AGAINST the efficacy of charges measured by volume (just as does moisture content) - because it is an inherent potential FAULT in that process.

The fact of inherent potential inefficiency with volumetric powder measurement technology is NOT somehow a "virtue". It is a PROBLEM.

Yep. The "proof is in the pudding". The powder charge contained in the "most accurate load" will WEIGH XX......and that will correspond to VOLUME YY ......EVERY TIME. Otherwise, it is an INVALID comparison. If the "most accurate" charge is determined to be 42.5 grains.....and your powder measure (or scoop) throws 42.6 grains due to moisture content or packing, etc. ....well then, said powder measure is INACCURATE.

As I said, the fact that a volumetric measure may SCREW UP, due to inherent problems with the methodology or even the technique of the operator, does not make that, by some bizarre logic, the "better" or "more accurate" means of measuring powder. The CORRECT charge is the CORRECT charge..... PERIOD.

Enough said. This is like arguing whether the sky is BLUE....and you are arguing that it really isn't "blue" because it is a different shade of blue that the shirt you happen to be wearing. BALONEY.

 

[Jimro]

wpsdlrg,

One of the most famous cases of "volumetric" charge dispensing being better than precise weighing comes from the Frankford Arsenal national match ammunition production.

It was found that for a certain year, volumetric charging produced a significant variation in charge weight with IMR4895, but that the volumetrically thrown charged ammunition had superior accuracy to the mass weighed charges.

There are very logical reasons for this non-intuitive result, but what it came down to is that with those components the volumetric measuring gave a more consistent dose of energy into the system. And this was with a relatively known single base stick powder.

When you get into double base ball powder I've personally found that exposure to moist air can cause the charge weight of a thrown charge to easily increase by half a grain for my 5.56 match loads. It is still delivering the same amount of nitrocellulose and nitroquanidine to the ammunition, the only difference is water.

If you have a an 8lb jug of powder, and you slowly use it up, the empty space in the jug will get filled by air, and that air will take up moisture, so your powder water content will change as the jug gets used. If you really want consistency you need to use the whole jug in the same loading session to ensure that weighing each charge is really measuring things precisely. Generally we find a charge weight that is tolerant of imprecision, so this isn't something people really worry about, but it is there and it is a factor.

Jimro

 

[hooligan1]

My Uniflow varies too much for me, with the powders I use mostly.
So I dump and trickle every load, I'm a "one at a timer", and don't care about speed.....just don't care...

 

[4runnerman]

Quote:
As long as the scale used to weigh the charges is accurate, then there is NO difference.
Except possibley for moisture content and packing.

Unclenick- Just trying to get a handle on this. If above you say is true. would that same powder not burn at a different rate as powder with less moisture,
Causing even a larger difference in MV?.

 

[1stmar]

Unclenick what are your thoughts on the following:
Normal powder charging time is 30min, powder remains in the canister until ready to begin charging
Environment is reasonably controlled (indoors ac/heat, closed room)
How much change is practical to effect volume during that reloading session?

Secondly cartridges are not humidically sealed, so i assume volume can change even after loading, no?

 

[Unclenick]

1stmar,

In a controlled environment, there isn't much problem. You are being pretty consistent with the energy dispensing part of the equation and only need to keep your technique consistent for the packing part. Quite a number of folks now dispense powder then put rounds in a loading tray setting on their vibratory tumbler to try to get even packing. I just haven't seen a systematic test of the results to know if it is to be recommended as SOP.

Some factories use military sealants, but there is no guarantee zero water vapor will permeate in or out. It will affect weight more than volume. This is one of a couple of reasons SAAMI reference ammunition lots get retested every two or three years to see if the pressure and velocity have changed. But the change is slow. I would not automatically trust match loads I've assembled not to change behavior a little over time and with additional transportation.


4runnerman,

Yes. That's what the Norma manual says. Burn rate changes with water content. They feel two equal weight charges of low and high moisture content powder do not behave the same, Wpsdlrg's statements to the contrary not withstanding. I'll let him argue about it with them if he wants to. I just didn't want to let his emphatically capitalized pronouncements be perceived as undisputed gospel by letting them go unremarked, and I think I've taken that as far as I need bother with. Some readers will be interested in the details of this sort of thing and some won't. That's normal.

Again, I recommend experimentation to learn the significance of the effects of these factors in your particular shooting systems with your particular component combinations. You can place powder in a Mason jar with an excess of desiccant to get it very dry. At the same time, in another jar, instead of desiccant put in a cup with some potassiium chloride no-sodium water softener salt in the bottom quarter of it that you have covered with water to get a saturated solution. That will regulate relative humidity at about 85% at room temperature, so the powder picks up moisture via the air without condensation drops forming on the inside of the glass that would directly wet the powder (this all assumes a constant or at least very slow changing temperature environment to prevent that). A saturated solution of potassium nitrate will get you 95% RH at room temperature in an enclosure like that, but it's harder to prevent condensation from small temperature changes then. If you want to try it, the kind sold for stump removal is fine for the purpose.

After a couple of weeks in the jars, load up two 10 round samples of each, one set by weight and one by volume for powder from each condition. See what your chronograph tells you about the differences in behavior and about which one gives you the most consistent results. Some people have a terrible time getting powder measures to throw consistently, and they may garner different results than you do, if you have a good touch with it.

 

[Sport45]

Volume is merely an indirect method to arrive at a certain weight, nothing more.

Or maybe weight is an indirect method to arrive at a certain volume, nothing more.

I dabble in sourdough bread baking. I can tell you from experience that four is difficult to consistently measure by volume as the amount of flour in a measuring cup is greatly dependant on how tightly it's packed. So I measure flour by weight. Most of the good cooks I know use volume measure for flour. Two means to the same end. If I want to get a consistent flour measurement I weigh it. The good cooks do just fine (better than me) with volumetric measurements.

In an extreme example consider the powder to be something like brown sugar. It has to be measured by packed volume. The weight of a fixed measure of brown sugar varies greatly with moisture content. So if my 1/2 cup measure weighs 20% less next week it doesn't matter. It's still exactly 1/2 cup of brown sugar.

 

[Unclenick]

And, if your are up on your Peter Reinhart, you'll know big bakeries test the water content of the flour to determine what that weight needs to be. I wish there were a simple way to do that with powder.