Powder measures, and volume vs. weight

[Dave R]

Most powder measures are volumetric. Uniflow, Autodisk, pretty much all of them except the electric powder dispensers with integrated scale, throw a charge based on volume, not weight.

Of course, you weigh the charge and adjust the volume to get the weight you want.

BUT....

What do you do when you have NOT changed the setting on the powder measure, and the next time you load, the weights are slightly off? I assume most of you adjust the measure again, to get the weight you want. That's what I do.

But is it the right thing to do?

What has changed? The volume probably has not moved, since you adjusted it. Has the powder become more or less dense? Probably. What else could have changed? So is the 'right' charge the one with the weight you now see, or the volume you had before?

You see where I'm heading. Should I set a volume once, and then never change it? Or continue to re-weigh every session and adjust the volume as needed?

I have heard that Lake City match ammo, and some other match ammo, is all loaded volumetrically. So will I get more accurate loads by sticking with a volume, rather than a weight?

 

[rogn]

W/V

Thats not an uncommon finding, most benchresters never weigh, theyll adjust small amts up or down to keep group tuned. If your loading anything on the higher end of the scale-hot loads- then use the measure togive you a base charge, just finalize each charge with the scale. Small vol cases such as pistol cases on the hot end then check and reset the weight each time you start loading. If youre in the midrange of pstol cases then 0.1 or so grain wont make a lot of difference.Its up to you. I usually reweigh and reset for heavy handgun or higehr end rile loads. Rmember its the actul weight of a powder charge that determines the amount of energy and/or pressure in the load.

 

[briandg]

I suggest that your problem may be that your fresh fill of powder is what makes the difference between your last load of your last batch, and your first load of your next batch. Try running 15 rounds of charges through the measure and dropping it back into the measure before you even try to weigh your loads.

The weight of the charge is what matters. the mass of powder is what turns into a cloud of gas. Volume of powder will not be consistent, only weight will give identical gas volume.

That's the theory, at least. Muzzle flash shows that the whole charge has not completely combusted, so it's hard to imagine that a person gets a consistent powder burn no matter how it is measured.

 

[TX Nimrod]

Muzzle flash shows that the whole charge has not completely combusted...

Once again this incorrect statement continues to spread around. The bulk of the muzzle flash is not unburned powder at all, but instead is composed of glowing gasses and/or gasses igniting when exposed to atmospheric oxygen. Perhaps the following site will help explain:

http://www.navweaps.com/index_tech/tech-090.htm



.

 

[WESHOOT2]

Use volume.

 

[wncchester]

"I have heard that Lake City match ammo, and some other match ammo, is all loaded volumetrically. So will I get more accurate loads by sticking with a volume, rather than a weight?"

No factory ammo uses weighed charges and much of it shoots quite well. Proving that some folks constant striving to scale charges to minute consistancy is almost laughable. Our cases vary more than such trival things can provide!

A LOT of reloaders don't weigh charges either but we all set our volumetric measures by weight. It's the mass of powder that does the job, not the thimble full.

 

[lmccrock]

What do you do when you have NOT changed the setting on the powder measure, and the next time you load, the weights are slightly off?

Some settling happens, and if the humidity is up, the powder may have absorbed some water, so do not store powder in the powder measure. Also, using Clays taught me to keep the press mechanism clean and smooth operating because any roughness causes the drop to be inconsistent. No such problem with 231, Titegroup, 2520, etc.

Lee

 

[Jim243]

I don't disagree, but where in the loading manuals do you find the "volume" of the load? All I see is the "weight", stated in grains. Lee's reloading manual is the only one that I know of that gives you the load by disk # or CC "Volume".



Jim

 

[Loader9]

I'm pretty much a volume loader. I have an RCBS powder measure that I had a cylinder made for it that is also calibrated. I use the measure to throw charges set at the calibration that I write down in the log book. When developing new loads, I throw the charges into a scale and develop loads from there. Humidity, temperature, and barometric pressure all effect a scale but the volume, if the temp is close to the same, is far more accurate.

 

[P-990]

I guess I load by volume. My normal procedure is to set the powder measure to throw the correct weight by checking on the scale, then I just load from the measure. Every 25 rounds or so, I check to see that the charge weight is still close (I accept .1 +/- as fine).

I work my up loads the same way, which I believe gives me loads with a wide sweet-spot for weight variation. Which works fine for me, because I really don't feel like trickling charges up to weight, even for 600-yard ammo. I'd rather be shooting! And yes, my un-trickled .223 ammo is capable of shooting around 1-MOA at 600 (proven by X-count), but the trigger nut sometimes loses it's torque setting by the end of a match.

 

[PA-Joe]

One thing you may want to try is to double tap on both the down and up strokes on the powder measure. That will help get a more consistent charge. Also each batch of powder will weigh different. So every time you get a new can you have to make adjustments.

 

[Dave R]

As usual, opinions differ. But it sounds like the safe course is to re-weigh and adjust for each session.

 

[Krieger9]

I weight but...

I weight everything because I can't wrap my head around the ideal of volume loading being more precise.

However I've read many times that a lot of precision shooters prefer volume loading. I think it's Richard Lee who in analysis states, "Volume loading Just works!". He went on to theorize that if the powder is packed tighter than it will burn and a different slower rate and lighter pack causes a quicker burn since the gases and primer flames can permeate better.

I doubt this holds well over large volumes but I think the theory is that slight differences in compression compensate the volume change.

As I said I can't wrap my head around it so I don't mess with it, but I do love theories.

 

[brickeyee]

I don't disagree, but where in the loading manuals do you find the "volume" of the load?

Outside of Lee dippers marked in cubic centimeters who cares?

Adjust the measure to throw the weight you want and go from there.

If you put a micrometer head on a Uniflow you can come back to the same setting again.

Smokeless powder is not especially hygroscopic, but it does absorb and release water based on the relative humidity causing the weight to shift.

Any remaining solvents from manufacture can also evaporate and alter the weight.

 

[zippy13]

The original LEE loaders were simple and inexpensive. They assumed their users wouldn't have reloading scales, thus their data was based on dipper volume instead of weight.

My metallic (Dillon) and shot shell (converted MECs) loaders all meter via adjustable volume bars, but I keep them honest with a scale. The tendency for one type of powder to meter more consistently (charge weight for a given volume) than another is of interest to reloaders with volumetric powder dropper. There's an active market in powder baffles because folks want more uniform powder drops. Of course, there will always those who prefer to meter by weight. This has spawned the merging of the electronic scale and powder dripper. You pays your money and you takes yer choice.