Temperature affect on POI

[Tmac]

I have a couple questions before my upcoming Colorado deer hunt. I live at 6500 feet, and will be hunting deer between 7K and 9K feet this year. I got a new gun this summer and have spent a lot of time shooting all year. I took it to the range this past weekend to verify everything was still dialed in and ready to go. I set up at 500 and used my app and boom, dead on at 500 yards. This is where i start overthinking things. It was 75 degrees where I was shooting this weekend. During my hunt temps will more than likely be in the 20's and 30's or colder. When I plug those numbers into my app I notice that my bullet drops a lot faster. that same dope at 500 yards could end up in a clean miss for me. Do you all make different dope cards for the conditions you will likely be hunting in, or am I overthinking this process? Would really like to hear what some of you more experienced rifle hunters do in these types of circumstances. I am an archer that does not gun hunt a whole lot. any help is greatly appreciated.

For my 270 Win, at 500 yards, going from 6,500’ at 75 degrees to 8,000’ and 25 degrees is just under 1/2”. Not enough to worry about. Assuming I did not fat finger a variable. The increase in altitude helps offset the lower temp I suspect, but at 500 yards it’s not a concern.

I’d just run a very simple ballistic calculator. It’s all that's needed to 500. Federal has a very simple one that has served me well to 600 yards.

 

[PNWGATOR]

To me, it’s not a matter of ‘not enough to matter’.

It’s about eliminating variables and correct data.

Simplicity.

 

[TaperPin]

I can't really uncheck consider powder temperature, when I am literally considering the powder temperature.

I'm not understanding how density altitude translates to this conversation specifically.

0° @ 1000ft is more dense than 0° @ 2400ft correct?

So in this specific instance we are taking a 100° swing at a specific altitude. I understand that could be interpreted to different numbers at different density altitudes (correct?) Just don't see how that is relevant to this topic.

But, I will try to learn more about it. If there's something I'm missing, please explain.

While H4350 may translate that way, as you even said it is one of the most temp stable powders. The exception, not the rule. I know Alliant Reloder powders are very temp sensitive.

Your ballistic calculator takes elevation and temp and computes density altitude for you. That chart shows how it changes.

You‘re around Boise so if you round up to 3,000’ in elevation, At zero degrees the density altitude (what airplanes or bullets think they are at) is right at sea level. Boise gets hot in the summer and at 100 degrees the air is now 8,000‘ density altitude.

 

[JF_Idaho]

@TaperPin

Thanks. Not familiar with the calculation, but do understand the premise.

Is it relevant in this particular instance? I'm not seeing how. But will take the initiative to learn how it is a better used calculation for firing solutions.

 

[JF_Idaho]

Ok, after double checking everything and realizing that a "2nd pair" in strelok was self generated without actual data I have corrected the temp sensitivity factor.

I will concede that with an extremely stable powder such as H4350 (calculated at .2 fps per degree) internal ballistics are slightly edged out by external ballistics of temp by roughly 1/4 moa drop at 500 yards.

But with a rough average of .8 fps per degree across powders (Reloder 15 calculated at 1.52 for example) internal ballistics have a greater effect on drop than external due to temperature as a generality atleast to the 500 yards we are talking about.

 

[ResearchinStuff]

Density altitude is simplest way to get the density of the air at the location you're in, which is important because that air density determines how much friction the flying bullet experiences, how quickly it slows down, and thus how much drop you have at various ranges. To get DA, you use a chart and 2 easily measured factors, local temp and actual Elevation, instead of temp, local pressure, and relative humidity. Charts are readily available online.