Cartridge temperatures

Bob A · #1 08-23-2017, 01:38 PM

Hi. I have not done any hunting yet, but I do like to put holes in paper. I'm not educated on cartridge or rifle design, however I met a very nice gentleman "qwert" at the range and he gave me some some very good advice on cartridges and rifles. Question. I read in a book that aa target hit bullseye at 700 hundred yards,if another cartridge was fired and the powder in the cartridge was 20 degrees warmer, the hit would be higher by 20". True or not. Thanks
Bob

fish_e_o · #2 08-23-2017, 01:42 PM

i've never had a temperature change of any sort change my poi by almost 3 moa

Bergerboy · #3 08-23-2017, 02:24 PM

Quote:

Originally Posted by Bob A

Hi. I have not done any hunting yet, but I do like to put holes in paper. I'm not educated on cartridge or rifle design, however I met a very nice gentleman "qwert" at the range and he gave me some some very good advice on cartridges and rifles. Question. I read in a book that aa target hit bullseye at 700 hundred yards,if another cartridge was fired and the powder in the cartridge was 20 degrees warmer, the hit would be higher by 20". True or not. Thanks
Bob

I tested my 22-250 at -20C then at +20C and the velocity change was 80fps. If I zeroed that rifle at 500yards the POI at 700 would change 3.6 inches with the 2 different velocities.
On a side note did the nice fellow you meet say "Your Mileage May Vary" after everything he said?

100zero · #4 08-23-2017, 02:25 PM

If the powder is not temperature stable a change in temperature will affect the muzzle velocity which will affect POI. Ill use my 6.5 load with 140 ELDm

On my load 700y is 110in drop at 23C, If i change only the temp to 0C my drop is now 113in. Thats with the same MV. Based on the article below you are looking at a 40FPS average temp change. So with my load at 0C and 40FPs drop in MV my new drop at 700 is 116in. So a total of 6in. It is a very efficient round with H4350, so a different cal will have different numbers. Thats potential a missed deer if i didn't account for the temp change.

http://precisionrifleblog.com/2016/0...s-imr-enduron/

gitrdun · #5 08-23-2017, 02:57 PM

Indeed "qwert" is a very nice fellow. He has a wealth of knowledge especially when it comes to reloading ammunition. I usually meet up with him at the various gunshows in Calgary.

Nyksta · #6 08-23-2017, 03:07 PM

It definately varies by powder and cartridge selected. But at typical hunting distances you probably wont need to worry about it. 100 feet per second slower velocity will give about 2 inches of change at 300 meters. And i doubt you would find a 100 feet per second change from extreme summer to extreme winter.

Smokinyotes · #7 08-23-2017, 06:17 PM

The last time i was shooting my 7LRM at 1100 yds i was dialling 23 moa. As the temperature increased and my ammo sitting in the hot sun, by the time i was done shooting 50 rounds i was down to 21.5 moa. Thats 17" difference in drop.

catnthehat · #8 08-23-2017, 06:43 PM

At !K we certainly notice a big difference as the sun starts to go down on the evening, but it is not only aiir temperature but barometric pressure and various other things as well that make up the differences in POI.
Cat

Bob A · #9 08-24-2017, 12:06 AM

Thanks for the replys. If I was hunting now I probably would not shoot at an animal over 150yards in any case. At that range,at a gun range I can usually place 3 shots into a 2" dia. circle.
I just wondered if the powder temp. did make a difference and if long range hunters took that into account. Thanks
Bob