Powders and temperature

[imr4198]

Fellow Weathbyterians,
   It seems that we all have a set of learned belief systems that we use to make sense of our reloading.  This primer is 'hotter', or that powder is 'slow'.  Some of the truisms fall short, however.  Every reloader knows that higher temperatures outside cause higher pressures, right?  Also lower temperatures will drop the pressure inside a cartridge case.  We do know that, don't we?  Maybe not.
   Here is data for the ever popular 30-06 cartridge with a 165 grain Hornady bullet.  Loads are identical for each powder (but will not be specified since this is not reloading data as such).  No the loads for AA4350 and H4350 and IMR4350 are not the same, just the same amount of let's say H4350 in three different temperatures.  Got it?  The base temperature is 70 degrees F.  Hot temperature for testing is 125 F.  Cold is 0 F.  Before you say IMR, 125 is stupid.  We won't be hunting in Death Valley.  It doesn't take much sun on an ammo box to reach these temps or more. Pressures are in CUP (copper crushers).

Powder-------------70---------125---------0
H4350--------------47300-----47800------48000
Re19----------------47200-----47800------48900
IMR4350------------51400-----50900------51700
VV N550------------50100-----60200------47600
AA4350   -------------47100------45100-----51900

   I imagine that knocks a few old wives for a loop.  The Vihtavuori powder had the biggest increase with hotter temps (10100CUP)  which is quite a lot.  The Hodgdon powder didn't change much.  H4350 uses the ADI so-called Extreme technology which negates a lot of the temperature induced pressure variations.  Did you notice how IMR4360 and AA4350 pressures actually went DOWN when they heated up.  Likewise the Re19 pressures went up in some cases when the temperature dropped (so did the H4350, and the other 4350's)
   How about the velocities? Well, let's take a peep.

Powder-----------70----------125----------0
H4350------------2881-------2880---------2884
Re19--------------2820-------2902--------2808
IMR4350----------2908-------2941--------2874
VV N550----------2883------2927--------2878
AA4350   -----------2786-------2772--------2801

   Velocities generally went up with higher pressures, but not in all cases.  Some of the velocities were lower with high pressures.  The IMR4350 data is completely upside down according to popular knowledge.  When the temps dropped for IMR4350 it caused the pressure to go up AND the velocities to go down.  Even the powder with the most extreme variation in pressures in this case (VV N550) doesn't produce a lot more velocity even when it is running at its highest pressures compared to the lower pressures.  If nothing else it does point out that drastically raising pressures doesn't always yield super high velocities. 
   Numbers are only good for this particular set of variables.  Like all data, it would look different with other conditions, bullets, primers, barrels, lot numbers, etc.  It does give us all something to think about however. 
your pal,
imr4198   

[eford]

Thank you for the great research and testing. I bet you liked doing it. 

I use Hodgdon's H-414, 4350, 4831, 4895, and 1000 powders and I like the fact they're resistant to temperature changes.  RL 19 does well also in 40ish degree temps, but that really isn't close to 0.

[Chip]

The more I know the less I know.

[grizzly340]

Yes Thank You for sharing your findings I use IMR 4350 in my 06 and am suprized I have read the volocity went up about 100 fps in warmer weather and have been waiting for cooler days to site in for deer season. this puts the wammy on that.

[bustinbirds]

Very interesting stuff IMR. I suppose this could cause a reload that was developed in June/July to change with regard to accuracy and performance by the time deer season rolls around in November. Did you notice changes in accuracy along with the changes in velocity?

[zonie]

Imr:   There's always some variations it seems.    We were discussing  similiar ideas awhile back, and while pressures may be the same,  velocities  can be different.     What program were you using ?    

[eford]

A hunting friend of mine spoke with a representative from Hodgdon's about the differences between H- versions and IMR powders. The rep said the IMR powders are more sensitve to temperture differences.

Getting off track a bit here, I wonder if the SuperFormance powders are sensitive like the IMRs are. Anyone know?

[bustinbirds]

Do you have reason to hypothesize that the Superformance would be sensitive to temperature?

[eford]

I don't have a clue if SuperFormance is sensitive to temps. Hopefully, it is not sensitive.

I will be one of the first in line to get the stuff if it's available for the 257 and 300 Wby. I think the powder has "raised the bar" in achieveable speed. Since it is loaded for the 25-06, 25WSSM, 300 Win Mag, I think there is a chance it will be blended / developed for the Wby cartridges across the board as well.

[terminator]

Hoping the same Eric.I would love to have some Superformance for the 257 and 300Wbys. IMR 7828 gives me high velocity but it is sure heat sensitive.The reason I have mainly switched to the Hodgdon Extreme lines.

[bustinbirds]

I thought it was strange that when they released the SuperFormance powder it was only for cartridges like the 22-250, 243, 300 wsm, and a few others when they had factory SuperFormance ammunition for a wide breadth of cartridges. I too would like to see a blend that is applicable to the '06 family of cartridges and the long magnums.

[NIK SOKO]

Good work IMR i've read a lot about temperature influence on loads and cold lowering pressure velocity etc but never any figures,i'm guessing those writers didn't actually do the cold test and probably wrote about it while sitting in front of the heater,as for superformance powder i'll just stick to adi powders and woodleigh bullets too
               Nik

[mike cardinal]

Mike sculked here and enjoyed the read.

[imr4198]

Australian Defense Industries did the lab work, not me.  Would anybody like to see a similar synopsis for the 300WinMag and powders like 4831?
imr

[terminator]

Sure thing IMR.Post it up.Very interesting.