H4350 Lot to Lot MV variation

[AlphaMikeBravo]

Has anyone tracked lot to lot variation in powders to see what an expected extreme spread in MV might be? I am new to reloading and was fortunate to start with about 10lbs of the same lot of H4350. I just started a new lot today and noticed my MV with the exact same load went down by about 37fps.

The only thing I can think of is that the humidity of the old lot has stabilized around 30% and this new lot is still more moist (have not had the opportunity to measure it) which would make it heavier and thus less actual powder by volume in my case.

If anyone has any ideas or facts about this I am all ears.

Thank you

 

[spife7980]

I don’t but test to see where it’s accurate.

 

[DownhillFromHere]

This description of moisture content effect on powder is interesting and may provide some info for you. It has been linked here before (which is where I found it). To me, 37fps seems like a noteworthy difference, even keeping in mind....

....My own experience with H4350 (and Varget... and 8208XBR... and N105... and CFE223... and H335... and........) is that I'll see as much as 10-15fps difference among "lots" of ammo comprised of the same exact components loaded on different days. For all that, I'll see a velocity difference in rounds of the SAME lot shot on different days even when temperature is similar or the same. I just chalk it up to cosmic rays or which way the headstamp was aligned in the chamber or other mysteries of the universe.

I found I needed to increase charge weight by a tenth of a grain to keep velocity the same when I moved from one 8lb jug of H4350 to another loading 6.5CM. Not much, and may well have been in the realm of cosmic ray effect or how many steps I took bringing the powder from storage cabinet to loading bench.

 

[lash]

This description of moisture content effect on powder is interesting and may provide some info for you. It has been linked here before (which is where I found it). To me, 37fps seems like a noteworthy difference, even keeping in mind....

....My own experience with H4350 (and Varget... and 8208XBR... and N105... and CFE223... and H335... and........) is that I'll see as much as 10-15fps difference among "lots" of ammo comprised of the same exact components loaded on different days. For all that, I'll see a velocity difference in rounds of the SAME lot shot on different days even when temperature is similar or the same. I just chalk it up to cosmic rays or which way the headstamp was aligned in the chamber or other mysteries of the universe.

I found I needed to increase charge weight by a tenth of a grain to keep velocity the same when I moved from one 8lb jug of H4350 to another loading 6.5CM. Not much, and may well have been in the realm of cosmic ray effect or how many steps I took bringing the powder from storage cabinet to loading bench.

You don’t have the correct cosmic crystals in your loading room…

 

[ShtrRdy]

Yes, different powder lots can have a different burn rate. You're thought about humidity is a good possibility too.

How much velocity variation would you see in your load with the original lot?

 

[XLR308]

You don’t have the correct cosmic crystals in your loading room…

Damn i better go check my Dylithium crystal supply before warp speed is unatainable.

 

[AlphaMikeBravo]

Yes, different powder lots can have a different burn rate. You're thought about humidity is a good possibility too.

How much velocity variation would you see in your load with the original lot?

Maybe 10-15 fps. I do think its humidity related now.

 

[AlphaMikeBravo]

Over the last 24 hours the humidity of that jug of powder has increased to 60%. It would make sense that this powder at 60% will behave differently than my powder that is down around 35%. I am surprised that a humidity change of 25% could change MV by 40fps.

My room stays around 25% all the time. I lived in a very arid area and my outside humidity rarely gets above about 45%.

My thinking is to keep my powder around 30%. If I do my load development with powder that is dry I should always stay safe with loads and loaded ammo should not vary much as it sits loaded and ready to shoot.

Next thing to do is dry the powder down to what my other powders are at and see what happens.

Appreciate the help.

 

[DeathBeforeDismount]

Dump it all into a bin, mix around then refill. Now all powder is same lot.

 

[DeathBeforeDismount]

Superlight scope doesn't help either.

 

[ShtrRdy]

Over the last 24 hours the humidity of that jug of powder has increased to 60%. It would make sense that this powder at 60% will behave differently than my powder that is down around 35%. I am surprised that a humidity change of 25% could change MV by 40fps.

My room stays around 25% all the time. I lived in a very arid area and my outside humidity rarely gets above about 45%.

My thinking is to keep my powder around 30%. If I do my load development with powder that is dry I should always stay safe with loads and loaded ammo should not vary much as it sits loaded and ready to shoot.

Next thing to do is dry the powder down to what my other powders are at and see what happens.

Appreciate the help.

Have you been reading up on this?

Here is one paper on some measurements that were done.

How does humidity affect powder?

You may have heard about a relationship between humidity and bullet velocity either in a book, on a reloading forum, or from a crusty benchrest shooter right after saying they get better ES/SD&#821…

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