New Jug Syndrome

[r3volut1oner]

I have a load that I use for about 300 shots already, measuring speed with garmin chrono almost of each shot.
Got stable 2608 average speed in temperature condition I am in.

This time speed went down to 2575 average, about 32 lower for 10 rounds I shot and measure.

Did exactly same brass preparations, I would consider no changes there as it's works for me for the rifle stable for last 6 months for sure.
The only difference was a new jug of powder I just opened.

Powder is StaBALL Match

Someone told me that he have it with Retumbo, with a new jug he just opened he had lower speed for the first batch of rounds.
And than even loads loaded next day don't have it, speed for the next batch of rounds comeback to normal.

And I realized that I seen it couple weeks ago with StaBALL HD, I am doing load development and for a new jug just opened and loaded cartridges I seen speed is lower, but wasn't sure if it's me did something wrong.

Does anyone having the same issues before? Maybe it's known issues I just not be aware of?
Looks like it's makes sense to open a new jug day before I gonna do powder measuring and pouring and bullet seating.

 

[Mike Casselton]

Did you account for ambient temperature differences?
It plays a big role in velocity.

 

[Rocketvapor]

Storage history and moisture content of old jug?

 

[ShtrRdy]

A couple things to consider with a new jug of powder.

If the new jug is a different lot number it likely will have a slightly different burn rate.

If where you live is considered a dryer climate, your old jug of powder will have dried out some which causes higher velocity. Then when you assemble a cartridge with powder from a new jug, the powder will have slightly more moisture and will burn slower.

What cartridge and bullet is this happening on?

 

[Doom]

"The only difference was a new jug of powder I just opened." Powder varies in burn rate and heat of explosion by lot. Even within a lot it may very slightly.

 

[lash]

I am disappoint. I taught dis was ‘bout breast augmentation…

But seriously, as each poster above has stated, a new container of powder can often differ in burn rate. In addition, local humidity conditions can affect powder burn rate.

 

[Holliday]

I often tweak my load a tad when I open a new jug to retain the same velocity. Usually just .02 grains or so. I thought that was pretty common.

 

[r3volut1oner]

Did you account for ambient temperature differences?

Yes, I had same conditions +-2 degree celcium

Storage history and moisture content of old jug?

It's beign stored in exactly same place, purchase from same shop.

 

[r3volut1oner]

If where you live is considered a dryer climate, your old jug of powder will have dried out some which causes higher velocity. Then when you assemble a cartridge with powder from a new jug, the powder will have slightly more moisture and will burn slower.

This is something that we actually where thinking about... and probably this is the case.
Reloading in apartment with heating with probably pretty dry air now, drying out the powder.

 

[r3volut1oner]

What cartridge and bullet is this happening on?

Happens on staball match 44.8 gn with .308 178 ELD-M
Also probably happened with staball hd 79 gn load 300 wm 208 eldm.

 

[Rodney65]

Did you account for ambient temperature differences?
It plays a big role in velocity.

I had a load shoot considerably faster in fairly cold (-5°F) weather, the opposite of what I expected. I attributed it to my chrono not working properly in the cold.

 

[r3volut1oner]

I often tweak my load a tad when I open a new jug to retain the same velocity. Usually just .02 grains or so. I thought that was pretty common.

So when you open a new jug, you basically add .02 ( maybe .2 grain? ) to the load to maintain same speed?
And later with same jug come back to the load you had before?

 

[Holliday]

So when you open a new jug, you basically add .02 ( maybe .2 grain? ) to the load to maintain same speed?
And later with same jug come back to the load you had before?

I check the speed with my chrono and adjust the load up or down accordingly. Usually it’s not much.

Yes you are correct .02 =.2 ….. Fat fingering keys again.

 

[lash]

This is something that we actually where thinking about... and probably this is the case.
Reloading in apartment with heating with probably pretty dry air now, drying out the powder.

This.

I think many reloaders don’t take the time to let the powder get to ambient conditions before using. I know that haven’t in the past.