Varget ?

[rebs]

If I worked up a 223 load using Varget in 70 to 80 degree temps how much will they be effected at 40 to 50 degree temps ?

 

[JimSC]

I would guess not much if your load is on a decent flat spot on the curve . According to this article Varget has .40 FPS per degree in temperature variance

Powder Temp Stability: Hodgdon Extreme vs. IMR Enduron

The goal of this field test was to quantify the temperature stability of the popular Hodgdon H4350 a...

precisionrifleblog.com

 

[RegionRat]

The best way to estimate your answer, is with a ballistics model that accounts for both internal and external ballistics.
For an 80 gr Berger VLD the difference from 80F to 40F at sea level is roughly 3 MOA at 1000 yards.

 

[searcher]

While I tend to shoot lighter .223 bullets (50-grain range), I do a lot of my range testing in the winter (30 to 50 degree) and most of my peak summer shooting is in pretty hot weather (85 to 105 degrees). If the numbers on the chart showing Varget as .40 fps per degree change - I'm thinking that may relate to "average" across many calibers(?), as my real-world experience shows the muzzle velocity drop to be about twice that. And that is on some pretty large volume of rounds over a chrono and many lots of Varget.

 

[Ned Ludd]

I wouldn't be surprised if you observed a decrease in velocity of 10 - 15 fps. Whether that would put the load "out of the window" is another question. It might, it might not. In my hands, loads developed at higher temperatures as you described still seemed to perform well at lower temperatures. However, the reverse has not been true for me. Loads developed at 50 degrees seemed to fall apart when the temps were in the 80s.

 

[K22]

I shoot and hunt all year ago using the same loads. I use the so called "temperature tolerant" Hodgdon's powers, i.e. H4895 and Varget.

For winter temps in the 30's to 50's to summer temps in the 70's to 90's I definitely experience point of impact changes being lower in the winter vs summer months. These changes vary approximately 1/2 inch to 3/4" in elevation.

I'm not sure but I suspect that most of this change is due to the changes in air density from winter, cold air being more dense, to the summer with less dense air rather than temperature affects on the powder.

The one type of powder I have experienced problems with in the past was with "ball" powders, namely H380 and H335 where I've had pressure surges in the summer months with temps in the 90's. While these powders produced excellent groups I move away from them and use "stick" powder exclusively now.

 

[JimSC]

well if the data from the article I linked at PRB was correct (80-40) x .4 = 16 FPS

 

[Texas10]

I put a tuner on my barrel, just for this reason. A small adjustment is all it takes.