Powder Temperature Sensitivity

[Guyotrd]

After finding out today that Alliant Power Pro 2000 has a 1 to 2 fps variance per degree F, I asked the Alliant guys which of their other products (almost all of them) were temperature sensitive and found out some of my favorite loads will have this problem (especially for my 6.5-06 which uses temperature sensitive RL 22 and I cannot jut go buy factory ammo) - As I hunt in Colorado there can often be a 60 degree difference where I hunt and the indoor range where I chrono - It was like finding out there is no Santa Claus.

My question is this - Which way does it effect - meaning does the shot speed up or slow down as it gets colder - or is it completely random? If I can factor this in then maybe I do not have to spend a year re-working all my loads with Hodgon and IMR new generation powders. Since we could be talking 60 degrees delta on 300 yd shots I would like to know.

As I think about it - how do I know what my factory ammo will do - as they do not disclose powder - I shoot a lot of Hornady ELD X - or am I over thinking this 1000th variable in reloading - or do I need to take my chrono out in the freezing cold and shoot.

 

[918v]

Generally the load speeds up as the temperature goes up. With some powders the speed remains stable in the cold, however, and then speeds up once you get past 70 degrees. With some powders, zero changes with temperature. It prints high in the cold and low when it’s hot, which counters the change in velocity. So the net effect is no poi change at all down range. You have to test your load and see for yourself.

 

[918v]

Oh, 2000MR in the 308 is a .6 FPS per degree powder, not 1-2 FPS. I dunno what your use for this powder is.

 

[Steel head]

You may find it’s not so bad as long as you’re not running a really hot load and/or seeing 80 plus degrees temps.
R17 and to a bit less degree R22 are like that.
Map it out and don’t get greedy.

 

[Guyotrd]

Oh, 2000MR in the 308 is a .6 FPS per degree powder, not 1-2 FPS. I dunno what your use for this powder is.

Thanks - it was Alliant Tech support that told me the 1-2 and as that is a 100% difference I tried to ask if it was one or two and he would not commit.

I am going to load 175 g Federal Edge TLR in my 308 piston gun with a 20 in barrel - It is a fast barrel that only loses 22fps on Factory 178 ELD X loads (I thought it would lose a lot more than the factory spec as they are generally optimistic and their barrel is 24 mine is 20)

I am chasing the federal max load for this of 2800 so the gun can stretch a bit longer for ELK - the 308 is marginal in my opinion for 300 plus yard shots on these big beasts. We hunt in the mountains overlooking valleys so the shots are always above 250 yds. I want a nice margin of error if I decide to take this gun.

 

[918v]

I got 2800 something with this powder and 175’s in a 26” Sako barrel. I tested it in the heat and saw no pressure issues. But my loads stay well off the lands and I don’t do stupid shit just to see what the limit of lapua brass is.

 

[Aftermath]

There is no Santa Clause? WTF, man!!!