Gun Hub Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
346 Posts
Discussion Starter #1
I don't understand what difference it makes, if any, between measuring powder by weight or by volume.
All load data in manuals is stated by weight, not volume.
Logic would tell me that, since the amount of space the powder takes up in either a cartridge or shotshell is important to uniform ignition, that volume would be important.
Also, I think that measureing by volume is more consistant, batch to batch. Weight can vary by lot and needs to be measured regulary, but a charge bar, once set, will throw the same volume.
If this is true, then what is gained by measuring powder by weight?
 

·
Registered
Joined
·
855 Posts
Loading manuals list powder charges in terms of weight because that is the way loads are developed and because mass is a more repeatable way to measure the absolute quantity of powder used for loading. A given mass can have different volumes, depending on conditions. Volume could vary due to settling, and I presume other factors such as ambient moisture. But it is the mass of powder, and not the volume, that is the more determinative factor in creating the working pressure in the cartridge.

That said, we use volumetric measures for loading cartridges in quantity because tools like powder measures and dippers can be set to throw repeatable volumes of powder far quicker than weighing each charge. Once a powder measure, or even a powder dipper, is calibrated to throw charges of a desired weight, they can serve to dispense the desired charge fairly well.

Some powders meter better than others. For example, ball powders typically meter better than flake, and both meter better than extruded (i.e., "rod" type, like IMR). At least that's my experience.

When set up properly, powder measures need to be checked every so often to make sure that they are still throwing the same weight charge as when they were first set up. Even though the volume is relatively constant, the weight can change as the powder compacts in the hopper and things settle in. A consistent technique for operating the powder measure also helps keep charges more uniform.

For most applications, reloaders can use a volumetric measure to load ammo. However, some match rifle shooters will weigh each charge to ensure total consistency. Even with hunting ammo, when using IMR powder, I will use a powder measure to throw a charge just below the desired weight, and then use a powder trickler drop powder into the pan scale to reach the desired weight. I just don't like the results of the throws I get with the larger IMR powders like 4350.
 

·
Premium Member
Joined
·
7,055 Posts
In the industry all powderis measured volumetrically and they have- or make- charge plates to accommodate whatever load is needed. But they still weigh them and pressure test frequently.

Handloaders can have volumetric measures like the RCBS Little Dandy that have a rotor that is calibrated for a single charge. In my early days I used that type until I could afford a Star tool.

Actually it might be easier to say that all powder measures are volumetric and are verified by weight.

But I suspect that the real reason that we use scales is because it is easier and more accurate than trying to use something like a graduated cylinder to get the volume. We certainly could do it in cubic centimeters- and in fact bulk density is measured in grams/cubic centimeter- but for the hobby handloader the scale is probably more accurate.

I weigh rifle charges too although there is absolutely no evidence to prove that accuracy is better when compared with charges thrown by measure by an experienced operator who does it exactly the same way every time.

Benchrest shooters hardly ever weigh chanrges and they're the pickiest bunch you'll ever see.
 

·
Registered
Joined
·
19 Posts
weighing powder in the grand scheme of things is relatively new. from day one until the development of smokeless gunpowder volume was used almost exclusivly for determining the amount of powder used. imagine carrying a set of scales on a battleground?

weighing is a more accurate way to determine the proper volume of powder needed.

lee uses volume is many of it's powder throwers.
RCBS uses volume in it's little dandy powder throwers.
 

·
Registered
Joined
·
430 Posts
Ammunition & Reloading

I use an RCBS powder measure to throw charges for rifle and pistol.

I usually load a block of 50 pistol cartridges or 20 rifle ones and then check every 10th or 15th throw. So far I haven't found my measurer to go off from where its set. Of course, it takes a while to set the charge but when it is set it's OK.

I don't do a lot of reloading, just what I shoot in a session on the range.

I have a MEC shot shell press for my wifes 20 ga; a Lyman EZ press for my 12 ga. and a Lyman Spar-Tee Turret press for all else.

Yeah, I know, they're old and slow but then so am I now. :sm_angel:
 
1 - 5 of 5 Posts
Top