Imr 4756 Temperature Question

[nhglyn]

I have seen differing opinions about the temperature sensitivity of 4756. Does anyone have the "definitive" truth?

Does the pf of a 38 Super driven by 4756 increase or decrease as the temperature rises? If I get a pf of 171 at 60 degrees, what will the pf of that same load be at 80 degrees?

Thanks for the information.

[al503]

I just chrono'd some rounds a couple of weeks ago in ~35-40 weather. I plan on doing the same (not so many different weights this time) again in the next couple of weeks (it's been around 50-60) lately.

From what I've read here, it is reverse sensitive (the colder, the hotter the load.) I've also read that some have seen noticeable variances from lot to lot, so that adds another dimension to it.

I've mixed a bunch of the powder together so that will take out at least one of the variables. I'll send you a pm when I'm able to get back out there to do another chrono session.

[Glen]

I have found that the power factor

goes down with increasing temperature.

Glen

[shred]

For me, it's reverse sensitive as Glen said-- temperature goes down, PF goes up. But.. everybodys load differs.

This is why you need to bring a small cooler to the range when you chrono. Fill it with ice and some sample loads (keep half at room temperature for comparison purposes). Throw in some drinks to keep the ice from rattling around. Chrono the ammo, drink the drinks.