Temperature to powder charge

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Camoman1

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I am in load development with my 6.5 creed in cold weather (-10c/-15c) , I have a real nice node with H4350 from 41.6-42.3 grains about .5-.6". I want to run around 42g, because 42.2 seems to be the tightest groups consistently under .5". I figure at normal shooting temps 42g should be more like 42.2. But in extreme heat I'm worried it will push me out of my accuracy node.

So really what I'm asking is anyone have real world experience with H4350 and how much powder charge is comparible to a particular change in temp?
 
H4350 = 0.16 fps change for each degree in temperature change, only Varget is less effected at 0.13 fps change for each degree in temperature change.

Remember many of the Hodgdon's powders are the "extreme powders" made in Australia. And also single base powders are more temperature stable than double base powders.

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I'm currently in the same boat as you... I did load development in -5c weather with 8208XBR. 8208XBR is suppose to be very temperature insensitive but so far I've seen a difference of 100fps between rounds that are out in -20c or in my pocket for 10 minutes.

I either got a bad batch of powder, my chronograph is on the fritz or XBR isn't as temp sensitive as advertised.
 
So to compare this to powder charge, how much velocity change does .2g of H4350 change velocity? Is the burn rate fairly linear and just divide (change in velocity/change in charge) to find FPS per grain? as per load data

I know this is not an exact answer just trying to get an idea...
 
Camoman1 said:
So to compare this to powder charge, how much velocity change does .2g of H4350 change velocity? Is the burn rate fairly linear and just divide (change in velocity/change in charge) to find FPS per grain? as per load data

I know this is not an exact answer just trying to get an idea...
Click to expand...

50 degrees x 0.16 = 8 fps, you are over thinking the problem. The U.S. military switched from RL15 to IMR-4064 for their long range 7.62 sniper ammunition. And IMR-4064 50 degrees x 0.45 = 22.5 fps.

You will just have to check your load in warmer temps and check accuracy and POI and see if it changes.

NOTE, forgive me if my math is incorrect, I didn't take my shoes off. :eek:
 
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