What impact does temperature have on velocity

N

nmibex

Guest
I'm working up a load for my 6mmAI (45.0 gr IMR 4831, 100 gr Sierra SBT, 3220 fps). I'm getting pretty close but the temperature today was 79 degrees. This is a hunting rifle and will probably be used closer to 50 degrees. Will the 29 degree temperature difference have much of a impact on muzzle velocity next fall?
 
Thanks

Thanks Al, I appreciate the response. I am going to have a BDC dial made for my scope. With that much difference in velocity I believe I’ll be better off to work up to 3220 fps next time the temperature is around 50 degrees in order to maintain accuracy and not to avoid the inch or so difference in bullet drop at 500 yards.
 
beer cooler

All you need is a beer cooler and a stick thermometer. Get a Blue Ice pack or two and put the thermometer in the bottom and blue ice on top cover with paper towels. Check the temperature in an hour.
On warm days take the cooler with the ammo in the cooler. Load from the cooler, check chronograph.
Centerfire
 
Thanks Centerfire

I'll give that a try . . . without the beer. In the past I've just quit tinkering with load development in the summer.
 
Temperature effects on Point of impact...

In 1988 I went to Canada hunting the last week of November. The week before I shot my 300 Win Mag and my 30-06 rifles. Sighting them both in 2.25" high at 100 yards. The temperature was approximately 55 degrees farinheight. After two plan rides and a temperature change to -14 degrees. Both rifles had point of impact changes more than 10 inches. The scope on the 30-06 a 3-9 Leupold would not adjust enough move the point of impact back to zero. Temperature effects primers, powder burn rate, barrel bore diameter, and scope internal parts.
Nat Lambeth
 
Rustystud said:
In 1988 I went to Canada hunting the last week of November. The week before I shot my 300 Win Mag and my 30-06 rifles. Sighting them both in 2.25" high at 100 yards. The temperature was approximately 55 degrees farinheight. After two plan rides and a temperature change to -14 degrees. Both rifles had point of impact changes more than 10 inches. The scope on the 30-06 a 3-9 Leupold would not adjust enough move the point of impact back to zero. Temperature effects primers, powder burn rate, barrel bore diameter, and scope internal parts.
Nat Lambeth
Click to expand...

Not to mention "tune."

I've watched 1moa hunting rifles wander around the target paper as much as 8moa while trying bullets and adjusting loads........ same bullet weight, just changing bullet brands and loads...... and all loads were grouping OK, just at different places on the paper. Now factor in the stuff Nat's talking about and it's a wonder eh!

al
 
Temp vs. velocity

Years ago, it was determined that a one degreeF would alter the velocity 1fps. That is how I remember it from many years ago!

Good luck,

Zeke
 
temp. & velocity

Speer used to publish a table in their loading manuals depicting a projected correlation between muzzle velocity and powder temperature with high velocity rifle cartridges. From zero to 100 degrees Fahrenheit, the difference was about 200 fps, up to around 3,500 fps or so. Beyond that the spread was somewhat greater.

Speer notes indicate the data was not based on actual firing. Whether or not such projections are valid today (or were even years ago) may be open to question.
 
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