Shooting pre-loaded ammo in hot weather?

[nonliberal]

I asked this on another forum as well but didn't get much response. What has the biggest effect on velocity due to temps? Is it the outside air temp, barrel temp (not including letting a round cook), or ammo temp?

If I wanted to use my regular load in hot weather (due to preloading) would I try to keep the ammo cool, super cool the barrel between relays, or just be out of luck because its the outside air temps that are killing me?

Depending on which load I use I am 55-110fps over what I developed the load to be due to the 100+ degree weather.

 

[BoydAllen]

Ammo temp.

 

[TheSnake]

I keep my ammo cool and try not to let it sit in the hot chamber too long before pulling the trigger. Depending on the outside tempature and or direct sun, that could be keeping it in the shade or in a small cooler if necessary.

You could also work up your loads using less powder for the hot weather.

 

[SDDasher]

I've noticed Quick Load is about .02 grains less for 10 degrees of upward ambient outside temp when using thier calculations.
Like a lot of hot weather (Fl & LA) shooters, I keep my ammo in a cooler prior to the match I am shooting and never leave it in direct sunlight.
I also agree, leaving a round in a hot chamber for very long is not a good thing for accuracy.
So I have a spring load and summer load that usually shoots consistently if I do my part.

 

[nonliberal]

Thanks guys! I will try the cooler and test over the chrono before the next match. I have 2 different loads and one is definately better in very hot weather, but that spring load is a tack driver when its cool enough to shoot. :-\

 

[nonliberal]

Well I decided today would be a good day to test with the 30x44 this time since its 105 degrees outside. I tried 4198 and H322. I loaded 10 rounds of each, 5 rounds stay on the bench outside in the shade and 5 of each were placed in a cooler with blue ice packs for 2 hours.

I shot them over the chronograph alternating between hot and cold so the barrel temps wouldn't screw with the results. None of the rounds were in the chamber for longer than 3 seconds.

The H4198 extreme averaged 3104 hot and 3065 cool for a 39 fps difference.
The H322 extreme averaged 2978 hot and 2957 cool for a 21fps difference.

It did slow the velocity, but in both cases the spread was larger with the ammo out of the cooler and accuracy was worse. This might be due to the fact that the ammo from the cooler instantly formed water all over the case and bullet from condensation even though it's only 24% humidity right now which is very low for us.

 

[TheSnake]

It did slow the velocity, but in both cases the spread was larger with the ammo out of the cooler and accuracy was worse. This might be due to the fact that the ammo from the cooler instantly formed water all over the case and bullet from condensation even though it's only 24% humidity right now which is very low for us.

Next time try to keep the ammo in the cooler just cooler and not cold. Use one one small ice pack and put a cloth over it. You don't want to simulate shooting at the North Pole.

 

[nonliberal]

It did slow the velocity, but in both cases the spread was larger with the ammo out of the cooler and accuracy was worse. This might be due to the fact that the ammo from the cooler instantly formed water all over the case and bullet from condensation even though it's only 24% humidity right now which is very low for us.

Next time try to keep the ammo in the cooler just cooler and not cold. Use one one small ice pack and put a cloth over it. You don't want to simulate shooting at the North Pole.

haha, ok I will give that a try.

 

[mikecr]

You know in advance it's gonna be Hades in July, right?
Doesn't make any sense to me that you would COOL ammo for this.

You can keep ammo near body temperature pretty much all year.
You could have developed loads with this.

 

[nonliberal]

You know in advance it's gonna be Hades in July, right?
Doesn't make any sense to me that you would COOL ammo for this.

You can keep ammo near body temperature pretty much all year.
You could have developed loads with this.

Thats true, I'm giving up on trying to use the spring and fall load in the summer. The accuracy difference isn't huge anyway.