Temperature sensitivity.

everypenny

Hi,
Can anyone tell me the temperature sensitivity of Hornady .308 steel match 165 gr ammunition.
Also, what is your understanding of the importance of the temperature sensitivity on ballistic software? (iStrelok)
Thanks.

Cass

Never used the steel match, but on Hornady 150 and SST 150 i found it is temp sensitive.

I once held a round in my hand, and my hand in my pocker, and waited for about 10-12 minutes for the ceasefire to end. I then loaded the round and fired it. There was a noticable difference in POI compared to the previous shots and the next round i fired that came from the box. So if the act of holding & heating it in my hand can affect POI what would happen with a round sitting int he chamber?

I already know that chambering a round for a long time in a hot chamber can effect POI. That is why when target shooting if you don't fire within 30-45 seconds you eject the round and use another. The point above is only to show that not only is a hot chamber an issue, but some can be sensitive to any prolonged change in temp however subtle.

Now this also relates to the temp of the day. During the winter months when temps are an average of 2-5 degrees i can see up to an MOA difference at all distances compared to the same results on a hotter summer day. Usually in the negative. IOW i need an extra MOA during the winter than summer. Also with the hot temps barrel heating happens faster and takes longer to cool.

For the purposes of target shooting everything comes into play. Temp, humidity, HASL, as well as the usual suspects of wind, etc.

everypenny

so when it comes to the data you'd put into a ballistic calculator what should I say?

For example iStrelok asks for a percentage value at a fixed temp. Its standard option is 2.5% at 30 Deg Cel. I'm assuming its the standard used through out the industry but should I just use this or is there a way of figuring it out specifically for that round?

Cass

I don't use Strelok so realistically anything i say might be wrong or incorrect for that program. The BC i've used ask for humidity, temp, HASL, speed, wind, angle of wind (value), scope height, etc, etc.

The temperature variances, of the air, do not affect me as much when i'm shooting through one season or the other. By this i mean with all the other details logged i get my zero and stay on it for months at a time. The variance in air temp are only a major factor if you exceed a large shift in temp. For example zero/shoot your gun in summer then don't shoot it again until the dead of winter and expect the same results. The same goes for altitude, but that's another story.

Have a read of some lads on Sniper's hide. They use it and seem to be more familiar with Strelok. I would sooner direct you there than give you some regurgitated information that i don't actually understand as i don't use it. http://forum.snipershide.com/snipers-hide-reloading/215260-strelok-temp-sensitivity-factor.html