Accounting for RL-15 / Temperature Swings

[Firearmsunlimited]

 

[Hoot]

No way AR-Comp has greater temp drift than IMR4064 and many of those others listed as lower than it.
AR-Comp spec is -20 to +160F temp change = 20fps velocity change in a 223 and 308. Certainly not .77fps/deg

Hoot

 

[SeabeeKen]

12 year old thread. What is the source of the chart?

 

[Gargoyle]

The barometric pressure and temperature of the rounds makes the biggest changes. Rounds matched to temp, like 20 F. and rounds sitting on bench at 20 F. before firing there will be greater velocity reduction than if you kept the rounds warm in the truck and shot out the window. To stay safe when load developing in the winter I will shoot out the driver's side seat with bag on the door. Then I can go to TX 80 F. and my pressures are similar. No surprises.

 

[Doom]

12 year old thread. What is the source of the chart?

I looked for the source way back when and never found this particular one. Whoever did it actually has the units incorrect. The correct units should be fps/degreeF.