Older powder question.....

Status
Not open for further replies.
Fatelvis

Fatelvis

Member
Joined
Dec 25, 2002
Messages
1,949
Location
Lockport, IL
I just pulled out my 550B toolhead that was set up for my .223 loading and checked the charge weight before loading. The powder measure has sat, untouched for over a year, (never changed the charge setting) as the RL15 powder has since last loading for my AR. Now the powder charge is reading .3 grns lighter than it was last time. Should I load "as-is", or turn it up .3 grns to meet my preferred 24.3 grns under a 69 SMK load? Thanks-
 
Same Powder?
Same scales?

If so, your powder has dried out, (either solvent or humidity), and doesn't weigh as much.

Or, if it's a new can of powder, it is from a different lot# and is blended to a slightly different density to get the same burn rate.

SO, crank it up to the 24.3 weight it is supposed to be.
We determine a smokeless powder charge by weight on a scale, not volume from a powder measure.

rc
 
I'm using the identical pound of powder that was last opened when I loaded .223 last. I'm using the same scale as last time as well. The powder must have dried out a little. So theoretically, if I bump up the charge a little, to meet the 24.3 target weight, it should have the same velocity/pressure as the last batch?
 
From behind the trigger I doubt you'd see the +/- 0.3 gr out of 24 anyway. It sounds like your powder is more dense than it was before assuming everything else is the same. If the powder measure is colder than it was the last time you loaded then the cavity may be a tiny bit smaller...
 
I agree Sport, but the "perfectionist" in me wants every round to show 0 fps SD, and 0fps extreme spread! Lol
 
Assuming the powder measure really hasn't changed and you have the same level of powder in it, your scale is telling you the same number of granules that weighed 24.3gr last year now weigh 24.0gr.

Is the energy in the weight of powder or in the volume of powder? This has been a long standing debate. Most of us, me included, would just dial the measure in for 24.3gr and get after it assuming the adjustmeny got bumped a tiny bit.

Or were you really at 24.2gr last year and still there this year and just seeing the +/-0.1gr tolerance in your scale? Have you tried check weights on the scale to see if it's really 24.0 now?
 
Before every loading session, (about once every 2 months), I re-calibrate my Dillon D-Terminator with the 50 Gm check weight. I even have the re-calibrating instructions laying under the scale, so I don't have to look for it....Like I said, I'm a perfectionist at times.
 
You know if it was me I would load up 10 and go see if the vel and accuracy was the same. If there was no difference I would load up the remainder. If there are problems then bump up the charge. This is how I learn what is not in the books.:D
 
rc nailed it. Burning powder is a chemical reaction that converts mass to energy in the form of a hot gas.

More Mass = More Gas

Use a scale to get the best measurement of mass
 
More Mass = More Gas
Click to expand...

What if the powder's density changes due to evaporation of the solvent? That stuff you smell when you open a jug of powder is volatile compounds leaving the powder never to return. In that case, the powder looses a little mass without a significant change in the gas produced when it burns.

Less Mass = Same Gas

Volume rules! :)
 
Sport45 said:
Less Mass = Same Gas

Volume rules!
Click to expand...
Time to rewrite the chemistry books. I doubt any of my college chemistry professors are still around to see this day.

:what:
 
But you are assuming the powder's chemical properties are fixed by its physical properties.

Take a brand-new 1# bottle of bullseye and measure 5.000 gr of powder. Put that powder in a empty powder jug, screw the lid down and set it aside for 6 months.

After the six months, if you dump every granule of that powder on your scale it may weight a little more (absorbed moisture?) or less (solvent evaporated?) than 5.000gr.

Has it gained energy if it absorbed moisture? Has it lost energy if the solvent evaporated?

I set my measure by weight just like 99+% of the reloaders out there. It's the best method available to me but I don't consider it to be an absolute. I do think it's good enough for me. :)

As for the OP, I think something changed in the powder measure that he is not aware of. And don't start re-writing your chemistry books yet. I said nothing that contradicts anything I learned from mine.
 
Last edited:
Another question along the same lines as above, do you know what the spread was last year? And what is the spread now? By spread I mean, what were the actual weights measured over, say, 10 charges?

To the point about recalibrating. Are you using an electronic/digital scale or a balance beam one? If electronic, are there any loud noises? When my tumbler is running, my weights can increase by 1-2/10's of a grain. [Best to not have any loud noises. The effect is not consistent.]
Also, with an electronic scale, good idea to recalibrate it before each loading session. Temperature can definitely affect the scale. Humidity might also.
I'm thinking a charge of RL 15 could easily vary by 3/10's grains. Even 2460 can have +/- 2/10's grain for a couple loads out of 25.
 
Should I load "as-is", or turn it up .3 grns to meet my preferred 24.3 grns under a 69 SMK load? Thanks-
Click to expand...

To directly answer your question: turn it up .3 grns to meet my preferred 24.3 grns under a 69 SMK load

That has always been my way and no problems.
 
While my Dillon powder measures seem to be excellent at throwing the same weight every round I check during the same loading session, I have never cam back to a previously set toolhead and not had to fine tune it a little. Crank it back up to where it is supposed to be.
 
Status
Not open for further replies.
Back
Top