Measuring Powder?

[chukarmandoo]

I am using the Lee Perfect powder measure and want some thoughts. I was reading that it is better to use volume than weight. I think the reasoning is that the burn rate is calculated by volume therefor it is more uniform from lot to lot, or even load to load? Does anyone have more input ? Thanks. Dan

[yobuck]

load 3 with your favorite load and shoot a group. then shoot 3 more 3/10 heavier at the same group and see where they land.
try 3/10 less also. then try 1/2 gr more or less.
we do all weigh our bullets and segregate those by weight dont we?
how about our cases, are they all uniform?
and we all bought a megplate trimmer didnt we?
whats that, you never heard of a megplate trimmer?
something else to worry about now that you have.

[darkker]

Go buy yourself a copy of Richard Lee's Modern Reloading Vol. 2. An excellent discussion on it.
For EXTRUDED powder only, burning rate is VERY closely tied to bulk density. Geometry is what controls the burning rate. Volume accounts for changing BD & BR. Weight only addressees the BD, and leaves you subject to a moving BR.

Ball powder is an entirely different animal. Due to consistency, you can certainly get away with volume (I have been for a VERY long time). However, if you are the toe that likes to run nuclear pressures as long as the bolt doesn't seize... Weight is more appropriate for you, when using ball powder.

[chukarmandoo]

Lee has always made loading easy and taken the mystery out. I could not grasp the concept of the c.c. dippers and did not use them. I guess mostly because I never had one that was the exact size for my loads. Well now with the amount of loading I have to do the Lee Perfect powder measure seems just fine I guess because 1 I hate loading and 2 it is fast.

[stangfish]

chuckarmando, great question. A few questions. How does the volume of each case effect the load? If the powder is mixed correctly, cut uniformly and then weighed identicaly, you could assume the volumes would be very similar. So for one important question is, how do I get my case volumes identical and my powder charges uniform.

So I start with using weight to insure uniformity of powder charge. With the case after proper prep, you can measure the weight of each and batch them as closely as possible. What you hope for with that method is to get your internal volumes close. Having to fill each one with water to determine its volume would get old quick.

[chukarmandoo]

chuckarmando, great question. A few questions. How does the volume of each case effect the load? If the powder is mixed correctly, cut uniformly and then weighed identicaly, you could assume the volumes would be very similar. So for one important question is, how do I get my case volumes identical and my powder charges uniform.

So I start with using weight to insure uniformity of powder charge. With the case after proper prep, you can measure the weight of each and batch them as closely as possible. What you hope for with that method is to get your internal volumes close. Having to fill each one with water to determine its volume would get old quick.

I probably not explaining this very well but the case has nothing to do with it. The only thing I talking about is measuring powder charge by cc (volume) instead of by weight (scales). Lee has a chart that shows cc=gr ratio for alot of powders. Does anyone know how commercial companies run their powder charges?
All I am saying is I heard or read that measuring powder charges by volume is better than weight because the powder is manufactured to burn by volume at a certain rate. therefore if one loads by volume than they can be less concerned about the powder from lot to lot.

[TC260]

For EXTRUDED powder only, burning rate is VERY closely tied to bulk density. Geometry is what controls the burning rate. Volume accounts for changing BD & BR. Weight only addressees the BD, and leaves you subject to a moving BR.

I'm not disagreeing with what you're writing here, just trying to piece it together. Bulk density is a variable measurement. It's not a material property so how are you determining BD from weight? 2nd ques, the "volume" of what and how are you measuring it?

[stangfish]

Sorry chuck. You explained it correctly. My thoughts were out of place. I used to get into things such as this and found it futile when I was looking for consistent .4 groups. I found the case prep with consistent weight loads to net me much better gains. I'm not a BR shooter though.

[CharlieNC]

Seems to me for a given "lot" of powder that the bulk density is consistent and therefore loading by volume or weight should render the same result. However weighing different drops from the powder dispenser does not give the same weight; this is because the volumetric metering device is not suitably consistent, so it is necessary to weigh each drop to achieve uniformity. Now when you change to a different lot of powder that is a new situation, but I'm not sure that either volume or weight is adequate if you are seeking perfection and it will be necessary to re-test the load for velocity and/or target performance.

[yobuck]

bottom line is accuracy. who cares about anything else other than whats necessary in order to achieve that.
there are other more important factors most dont even think about.

[darkker]

Does anyone know how commercial companies run their powder charges?
We (the reloading market) are entirely built as a waste market. Folks such as Hodgdon buy surplus powder in various lots, blend it for a relatively consistent burn rate; then sell it. As an example H335 and Bl-c(2) come from the EXACT same parent powder (specs are wide ranges). Tell a handloader they are the same and they will lose their mind, but it's the truth. Handloaders RARELY have a Pressure Trace, or other device to test and adjust accordingly. None the less, NORMAL burning rate variation is 5%. Meaning that " drop 10% and start over" warning that everyone posts is a VERY real possibility. There is NO commercial ammo manufacturer in the US that loads by weight, it is all volume.


I'm not disagreeing with what you're writing here, just trying to piece it together. Bulk density is a variable measurement. It's not a material property so how are you determining BD from weight? 2nd ques, the "volume" of what and how are you measuring it?

BD is a weight measurement of the nitroglycerin in a powder, or amount of energy in a powder. Yes it does vary, but the changing geometry will adjust the burning rate in an appropriately safe manor. The volume of a powder is totally independent of its weight, think of whole wheat flour. A cup is a cup of flour, regardless of what it weighs.
The charts that Lee gives are references ONLY!. If you are looking for a starting point, do the VMD calculation he describes, to get a basis for your specific lot of powder.
Case volume ALSO determines actual burning rate changes. Which is another reason keeping the case VOLUME the same will aid consistency. A weight of powder, has a variable volume; less consistent.

Again there is a very good discussion, and confirmation by powders companies in Lee's book. Does that mean volume is the only way to go? Certainly not! But once you understand how powder is built (who builds it, for what purpose), how it is designed to work; it makes life easier and leaves less to the imagination and sorcery.

A similar fun activity to try at home:
For those that WEIGH their brass, hoping to guess the volume... Take a handful of all of it, do your weight trick, but then ALSO actually measure the VOLUME of all that brass. It's going to mess-up your way of thinking about weight telling you volumes :-)

[chukarmandoo]

Well Darkker thanks for your input. The last few loading sessions I have ran my powder charges using the "LEE PERFECT" powder measure and my groups are looking good and most of all it saves me a lot of time. I don't get to be a better shooter because I have a lot of loading time. I only shoot better with a lot of range time! If I had the money someone else would be loading for me. LOL. Thanks. Dan

[TC260]

BD is a weight measurement of the nitroglycerin in a powder, or amount of energy in a powder. Yes it does vary, but the changing geometry will adjust the burning rate in an appropriately safe manor. The volume of a powder is totally independent of its weight, think of whole wheat flour. A cup is a cup of flour, regardless of what it weighs.
The charts that Lee gives are references ONLY!. If you are looking for a starting point, do the VMD calculation he describes, to get a basis for your specific lot of powder.
Case volume ALSO determines actual burning rate changes. Which is another reason keeping the case VOLUME the same will aid consistency. A weight of powder, has a variable volume; less consistent.

I guess I'll have to read the book. Using terms in the abstract without explaining what they mean is difficult to follow. VMD calculation? I could hazard a guess that that stands for volumetric mass density calculation? Intuitively that would make more sense to be calculating actual density rather than bulk density but...

[chukarmandoo]

VMD = volume measure density. Volume of 1 grain of powder.

[TC260]

Thanks. I did a google search and found VMD as it's being used here. This thread seemed to make the simple complicated :p. With a science/engineering background sometimes I tend to read too deeply into what's being written.

[chukarmandoo]

Okay, I been doing some testing , sort of. I always hear about different loads and how they react in different guns. For years I shot only factory loads and was always happy with the results. Even in the Corps we all qualified with factory ammo. Like 280 of us at a time and some shot really bad and some shot really good. So when I shot really good when ever I shot I now think it was just luck? I must have gotten a really good rifle or a really good batch of ammo (the same that everyone else was using)? Or I always got a good rifle and good ammo? I'm saying all this because (when loading) how good is good enough?
So saying all this is the info that we get from each other not accurate because most of us weigh are loads and most have different lots of powder? For example I have been using a beam scale and running 43 grs of H4350 and my speed is 2775 out of a 26" barrel. Now the last two shoots I've just thrown my loads after I set my powder thrower to my scales. We never get any spotter rounds so we go with what zero we have. So I think my stick is really slow. Now to today I set up the thrower to throw a charge of 43 grs. by volume and when I go by the chart from Lee .0725 x 43 I get 3.1175 and round it off to 3.12. Then I throw some charges and guess what. They are 43.6 grs. Now if I run this load is it 43 grs or is it 43.6? If it is really 43 grs. I would expect my fps to be up there with most other guns.
I'll be headed to the range this week and I run some weighed charges and some thrown charges and post the results.

[darkker]

I think you got lost in translation. When using volume, weight is used as a reference ONLY. Don't concern yourself with it past that. Rounding up the cc's will change the weight anyway. Remember you are after a volume, not a weight. Depending upon how old the Lee chart is, I would ignore it, and use a VMD calc for your specific lot.
Let us know how it goes for you.

[chukarmandoo]

darkker this is what I done. I read under calibration to set my powder measure to a large whole # so I set it to 4 then I calibrated my scales to zero. Then I dumped a charge of powder and adjusted scales till it read a certain weight and then divided 4 into that # and came up with a # like .07024xxx which then became my volume for 1 grain of powder. So now I just multiply that # by the grains I want and dial that total on my powder thrower. The # was less than the chart but is GTG for that lot according to Lee. I can actually get a good reading with a little experimenting.

I also read a very good article about load development and was pretty impressed so now I do so loading. Starting from scratch.

[MacDR]

The perfect powder measure is great but like all measures of its type both consistent operation and smaller grain powders lead to repeatable accuracy. The reason is simple. Small grain powders especially ball and flake settle into measure with little airspace between grains. They tolerate inconsistsnt operation of the measure. Larger extruded powders tend to bridge and settle with more airspace between grains. Consistent operation of the measure is much more critical to getting consistent throws. Try this experiment with an extruded powder. Tap the lever twice at the top of travel on one throw and just barely on the next. The first throw will be heavier and consequently of greater volume than the second one. Try the same with a finer ball powder and you will find much less difference between the two throws. In practise, I measure by weight every throw for target shooting accuracy and, after setting the measure by weight, load by volume for hunting and plinking.

[BillPa]

Consistent operation of the measure is much more critical to getting consistent throws.

As does using a baffle to help keep the powder weight reasonably consistent filling the chamber by eliminating the weight of the powder above it in the reservoir. http://www.allmantrading.com/reloading/baffle.pdf

Bill