temperatures effect on everything.

[chevytruck_83]

I see posts about how temperature sensitive a powder is but often wander how much effect the barrel being subjected to the same Temps effects velocity. I realize the expansion of steel is very minimal but I would think there is some change. A tighter bore at least In my head would cause both higher pressures and more resistance. Are there any articles worth reading that take other factors into account when considering temperature.?

 

[chkunz]

All powders are temperature sensitive. I have found a few references that give some information on this. Most of what I have found shows about 1.8 feet per second velocity change for each Deg of temperature change. When I chronograph rounds I try to do a good job of estimating the mean bulk temperature of the powder (not just the ambient temperature) and correct to a nominal temperature that I have chosen. For simplicity I have rounded this correction off to 2 feet per second per degree.

 

[M-61]

Quote from chkunz
....."Most of what I have found shows about 1.8 feet per second velocity change for each Deg of temperature change.".....

Does that mean an INCREASE or DECREASE in temperatures? And from what base number?

 

[dkhunt14]

In my testing the colder it got the more the velocity dropped. I can't remember the numbers but I tested Varget in a Dasher. In 15 degrees I believe it was around 20 feet. Matt

 

[chkunz]

Quote from chkunz
....."Most of what I have found shows about 1.8 feet per second velocity change for each Deg of temperature change.".....

Does that mean an INCREASE or DECREASE in temperatures? And from what base number?

Increase in temperature results in an increase in velocity. Decrease in temperature results in a decrease in velocity.

 

[chevytruck_83]

For the sake of argument that would seem to follow the theory that a barrel contracts with a lowering temperature.

 

[savagedasher]

Increase in temperature results in an increase in velocity. Decrease in temperature results in a decrease in velocity.

Some powder has a bigger difference in speed then others . Normally cold has less effect then heat. Larry

 

[Joe Salt]

Kind of makes sense to me if you use a hot load in hotter temp. your definitely going to gain in velocity.And powder does make a different between lot#'s

Joe Salt

 

[savagedasher]

Kind of makes sense to me if you use a hot load in hotter temp. your definitely going to gain in velocity.And powder does make a different between lot#'s

Joe Salt

Hogdon state their extremely 4831 sc has 10' difference from 0 to100 Imr 4831 is in excess of 100' . Larry

 

[fx77]

There may be an average change but it is not necessarily linear

 

[chkunz]

For the sake of argument that would seem to follow the theory that a barrel contracts with a lowering temperature.

The coefficient of linear expansion for steel is 0.0000065 in/in/deg F so you can ignore the effect of temperature on barrel dimensions.

 

[chkunz]

For the sake of argument that would seem to follow the theory that a barrel contracts with a lowering temperature.

The burn rate of powder changes with temperature and that is what gives a change in muzzle velocity with temperature.

 

[chkunz]

There may be an average change but it is not necessarily linear

I have an interest in this, do you have references? Data?

 

[savagedasher]

I have an interest in this, do you have references? Data?

Check Hodgon . Larry

 

[chkunz]

Check Hodgon . Larry

Will do, thanks. I have been using "Hatchers Notebook" mostly.

 

[chevytruck_83]

I realize it's not a fair comparison but anyone that's put a sealed bearing in the freezer then heated the housing it's going into knows that even the smallest expansion and contraction can be a factor. Again I realize that taking a bearing up to say 300 and the housing down to 34 is not at all the same thing. Was just wandering if there has been any legitimate tests don't to test it's effect. Cold temperatures is definitely enough to effect the gun mechanically.

 

[LHSmith]

The coefficient of linear expansion for steel is 0.0000065 in/in/deg F so you can ignore the effect of temperature on barrel dimensions.

Exactly right. Plug in temp differential and even using a 100' swing the change is extremely small.

 

[chkunz]

I realize it's not a fair comparison but anyone that's put a sealed bearing in the freezer then heated the housing it's going into knows that even the smallest expansion and contraction can be a factor. Again I realize that taking a bearing up to say 300 and the housing down to 34 is not at all the same thing. Was just wandering if there has been any legitimate tests don't to test it's effect. Cold temperatures is definitely enough to effect the gun mechanically.

First let me say that I am not disagreeing with you that temperature can have effects on a guns performance in many ways. We could research government testing on military weapons and learn a lot. In your bearing case you could expect something on the order of 0.002 inches expansion per inch of steel for the 300 deg temperature difference and as you experienced that was significant. Now I am not saying that temperature effect on the gun steal is not a factor, I am just saying that we know the thermal expansion of the steel very well and we can estimate what that would be with a rifle. I remember reading once where a hunter experienced a failure to fire in the cold while hunting due to the grease reaction to the cold. I do enjoy thinking about such things.

 

[savagedasher]

First let me say that I am not disagreeing with you that temperature can have effects on a guns performance in many ways. We could research government testing on military weapons and learn a lot. In your bearing case you could expect something on the order of 0.002 inches expansion per inch of steel for the 300 deg temperature difference and as you experienced that was significant. Now I am not saying that temperature effect on the gun steal is not a factor, I am just saying that we know the thermal expansion of the steel very well and we can estimate what that would be with a rifle. I remember reading once where a hunter experienced a failure to fire in the cold while hunting due to the grease reaction to the cold. I do enjoy thinking about such things.

I had my gun when we went to Michigan and the temperature was around zero wouldn't shoot . The primers weren't mag . Larry

 

[dkhunt14]

I had my gun when we went to Michigan and the temperature was around zero wouldn't shoot . The primers weren't mag . Larry

Could have been the cold didn't let the firing pin hit hard enough. I had this happen in a banquet shoot when it was bitter cold. I had to hit the first three, two or three times to get them to go off. After a few fired and I got some heat in the gun they all fired. Matt