Let me see if I can ask this question where it makes sense. I have always been told that ball powders were more heat sensitive than stick powders. Our high power team shoots nothing but stick powders due to this situation.
My question is this. When we shoot rapid fire our brass is getting really hot, that heat is being transfered into the powder before the next round is fired and through the entire string the chamber is adding even more heat to each succesive round. The heat from the chamber to the brass has got to be really fast as I recall "cooking off" rounds on full auto in the army.
When we fire rapids in cool weather, say 60 degrees and we're using ball powder how come it isn't eratic when it's being heated up in the chamber anyway. The heat of the round sitting in the chamber is way higher than it would be just sitting in the summer sun.
Have any of you actually tested out the variations in accuracy of ball versus stick powder in various temperatures.
Does this question make any sense to you?
I just can't see that the ambient temperature of the round in the sunlight would cause a powder to react differently than when it is heated up by another source (the chamber).

I haven't seen any convincing evidence that any commercially available powder is insensitive to heat, although it continues as one of the great firearms related myths. I have however read the results of more than a couple of carefully controlled tests that suggest that all powders are heat sensitive. I don't know that ball, flake, or stick powders have any potential accuracy difference. I suppose if all the benchrest folks are using one type of powder, there's a time tested reason for doing so. Also, you don't mention how long the rounds are sitting in the sun as opposed to inside a chamber. It does make a difference.

quote:

Have any of you actually tested out the variations in accuracy of ball versus stick powder in various temperatures.
Does this question make any sense to you?
I just can't see that the ambient temperature of the round in the sunlight would cause a powder to react differently than when it is heated up by another source (the chamber).

I haven`t looked at the difference in heat on any powder types in any real meaningful way but I have noticed all powders show velocity variation with temps over say 60-70 F and up where some powders show less in velocity variatiuon from 60-70 down to 20 F or lower.

The fact that heat is heat leads me to believe though that the difference from sunlight or chamber heat bleed off to your ammo is going to cause the same variation as long as the temps are the same. How much heat will tranfer to your cartridge from each source will of course vary. The heat from fireing IMO likely can get much higher then from sunlight if enough rds are fired fast enough without allowing the chamber to cool.

It would be easy to set a crony up during one of your rapid fire strings to see if the last rd is showing any velocity change and how much if so from the norm.

If you shoot rapid fire, you need to use ball powder, because they burn cooler!

quote:

Much has been made about ball powders being cooler burning than extruded powders, but the fact of the matter is that there really isn't much difference. Flame temperature is very close to the same for all smokeless powders and runs about 3300 degrees F. Ball type powders tend to be from 3200 to 3300 degrees F and extruded powders tend to run 3300 to 3400 degrees F but there is wide variation

From this artical; http://www.frfrogspad.com/intballi.htm

I have some old Norma data showing the pressure vs temperature in a 30-06.Definitely happens !! The caution is that if you are using max loads -do not work up max loads in the cold weather and use them in warm weather !!!

I was out shooting some pistol loads over the Oehler last Sunday. Temps were in the high 30s. Every first shot from a cold pistol was 30-50fps slower than the 2nd shot from the now warm chamber. I have also seen some of my rifle loads vary as much as 100fps from temps in the 30s-100deg. So there is definetly something to powders being at least somewhat sensitive to temp. variations.