Range Report Temperature of ammo

[Timl]

I live in the Pacific Northwest. I still try to shoot thru the winter months (when it's not raining). But the typical temperature is 30 to 40 degrees. What do you do with he ammo at the range? Do you keep the ammo warm somehow or just shoot cold ammo?

I purchased a new rifle (300 Norma mag) and are working on loads. This is new for me so I'm trying to make sure I don't do something stupid that will slow the process.

Thanks for your help.

 

[Aimsmall55]

Re: Temperature of ammo

Get the hodgdon extreme line powders. H1000, h4350...... They are well known for their temp stability.

 

[Hookturnr]

Re: Temperature of ammo

Agreed with Aimsmall, the extreme powders are much more stable than most but you will find different rates of stability so you may want to try a couple different ones.
I'm running H1000 in a 300RUM with a 7fps average difference at 30 degrees versus my load development temp of 75 degrees.
In that same rifle with retumbo, I was getting 20fps average change. That's still markedly better than the 105fps loss I got with RL25!
I prefer to develop my load in 75-80 temps as it's typically the hottest temps I'll be shooting in and then check for velocity change on a couple 30 degree days and go from there.

 

[Bob 964]

Re: Temperature of ammo

As temperature decreases, the air becomes more dense and your bullet should fly less efficiently and with a lower velocity. If you zero your weapon at 60 degrees F and fire it at 30 degrees F, the increased air density should cause the bullet to fly slower and have a lower POI on your target. If temperature goes up, impact goes up; if temperature goes down, impact goes down. Generally speaking, cold ammo doesn't perform as well as ammo at higher temperature. Higher temperature generates higher pressure, which generates higher velocity.

I remember seeing a formula that permits you to adjust for temperature.

Degrees +/- from 60F X Target Distance in Hundreds of Yards / 10

So... if the temperature is 90 degrees and I am shooting at 500 yards, I would subtract 60 from 90 and multiply this number (30) times 5, and then divide the result (150) by 10. The result is 15. So I would subtract 15 from 500 and adjust my scope as if I were shooting from 485 yards. If the temperature is 30 degrees and I am shooting at 500 yards, I would subtract 60 from 30 and multiply this number (-30) times 5, and then divide the result (-150) by 10. The result is -15. So I would add 15 from 500 and adjust my scope as if I were shooting from 515 yards.

If nothing else, it's an interesting happy hour discussion topic.

 

[korykhunter]

Re: Temperature of ammo

If you find a good load now make sure you use caution when it warms up. Keeping ammo in a cooler in summer is not a bad idea.

 

[Timl]

Re: Temperature of ammo

Kory
It was 37 degrees when I did my load testing, but I kept the ammo in a cooler with a few hand warming thingys, to try and keep the ammo around 55 to 60 degrees. I think it worked out ok.

 

[The Mechanic]

Re: Temperature of ammo

Could always keep em' in your pocket.

 

[northern50]

Re: Temperature of ammo

Tomorrow it will be a high of 13 degrees F. I'll be shooting. Usually I'll just shoot the ammo at whatever temperature they come out of the box at. Tomorrow I'm load testing for the .260 so I'll probably keep them on the dash of the truck and in my pocket while I'm shooting.

As others said, find a powder that is temp sensitive and you are good to go. Usually you will see slower velocities and lower pressures in the cold.

Remember if you build a load in the cold just note it could be a little hotter in the warmer months. Keep that in mind when you reach the top of the scale on the max loads.