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Topic: Powders And Temperatures (Read 868 times) previous topic - next topic

Powders And Temperatures

Gents:  This was on Weatherby Nation several years ago but I think it might help clear up some questions about how certain powders perform at mild, cold, and hot temperatures. A big takeaway from this is H-4350 delivered consistent velocities. What more could you get from an over-the-counter powder?

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. 
Of all the gin joints in all the towns in all the world, she walks into mine.
Every man has got to know his limits.

Re: Powders And Temperatures

Reply #1
Thanks for digging that data up!  It's been some while since I'd seen it, and frankly I'd forgotten about it.
Do you know the protocol in detail?  Specifically, was it only the cartridge that was heated and cooled, or was it also the firearm?

Re: Powders And Temperatures

Reply #2
MZ5: As best I remember, the cartridges were cooled in a freezer, then kept in a cooler until right before they were fired. I don't remember how the cartridges were heated. I also don't remember how much time was taken between shots or how the barrel was cooled.
Of all the gin joints in all the towns in all the world, she walks into mine.
Every man has got to know his limits.