Temperature and trajectory

[Harrynsw]

Hi Folks
Have never taken serious consideration in this regard, but now I'm thinking it is a big deal. If I'm at the range I'm a cool morning (say 9 degrees) and zero my .223 in at 100m, 6 months later when I'm shooting at temperatures of 35 degrees, how much will that move me off my 100m zero?

[TassieTiger]

This is free and will answer quite a few Q’s

https://itunes.apple.com/us/app/sniper- ... 1026883819

[Aliqua]

This is free and will answer quite a few Q’s

https://itunes.apple.com/us/app/sniper- ... 1026883819

Disclaimer: Android user. Clicked link out of curiosity, $15.99

[SCJ429]

Part of the variable is the powder you are using and its sensitivity to temperature. It can push you out of your node easily. ADI has put a lot of research into this and are a world leader in this regard.

[TassieTiger]

Well that will teach ya Aliqua.
It’s def free on iPhone.

[brett1868]

Many of the old pro shooters had a summer and winter load to compensate for the temperature. This was more important back then as the powders were not temperature stable, unlike modern powders that are. That being said I still take 3 different loads to each competition and try each before deciding which to use for the match.

[Harrynsw]

Many of the old pro shooters had a summer and winter load to compensate for the temperature. This was more important back then as the powders were not temperature stable, unlike modern powders that are. That being said I still take 3 different loads to each competition and try each before deciding which to use for the match.

Hasn't it got to do with air density also?

[straightshooter]

Hi Folks
Have never taken serious consideration in this regard, but now I'm thinking it is a big deal. If I'm at the range I'm a cool morning (say 9 degrees) and zero my .223 in at 100m, 6 months later when I'm shooting at temperatures of 35 degrees, how much will that move me off my 100m zero?

All ballistic modelling relies on standardised parameters.
Variations in "air density" due to temperature, elevation or humidity will have an effect that might not be easily quantifiable, but might only be noticed at long range or sometimes one variable may offset another variable for no tangible effect.
So in your example the answer likely is: Not enough to worry about!
Be aware that many commenters are preoccupied with trivia whose effects are one or two orders of magnitude less than the fundamental aspects of shooting accuracy. This commentary often serves to confuse rather than enlighten.

[TassieTiger]

All ballistic modelling relies on standardised parameters.
Variations in "air density" due to temperature, elevation or humidity will have an effect that might not be easily quantifiable, but might only be noticed at long range or sometimes one variable may offset another variable for no tangible effect.
So in your example the answer likely is: Not enough to worry about!
Be aware that many commenters are preoccupied with trivia whose effects are one or two orders of magnitude less than the fundamental aspects of shooting accuracy. This commentary often serves to confuse rather than enlighten.

What if those variables all align vs cancel each other out? Ie shooting east vs west at a long distance, And/or using one load at sea level vs 600m - then, Combining 600m vs due east when practice was at sea level due west...add in a combination of hot / cold powders, density, etc
Edit - soz, just re read parameters - 100m is moot.

[Sergeant Hartman]

Hi Folks
Have never taken serious consideration in this regard, but now I'm thinking it is a big deal. If I'm at the range I'm a cool morning (say 9 degrees) and zero my .223 in at 100m, 6 months later when I'm shooting at temperatures of 35 degrees, how much will that move me off my 100m zero?

As some of the more seasoned shooters have said. Temperature and humidity play a small part which gets more significant with distance (or benchrest type competitions). If your shooting close or hunting larger animals close it doesn't matter that much.

Also most powders are sensitive to temp and humidity while ADI's biggest marketing strength is their (relative) insensitivity to temperature. Something that they advertise on every bottle of powder and all their ammo boxes. Obviously if you buy commercial ammo then their results will vary due to the powder used.

My old friend who has been shooting for 40/50 years has one load that seems to work for him throughout the year and surprisingly in multiple rifles. So much so Using his standard load another friend consistently shots 0.5moa in his tikka 6.5 creedmore.

Now the app while a great tool will not tell you the effect the type of powder you use will have on your groups.

Aliqua, mate i found the best app is the hornady ballistic calculator. It has a standard ballistic calculator and the 4dof calculator that even takes into account things like corolis effect to give me a set of numbers that will get me onto the 500m big plate at little river. And best of all its free.. search for it in your app store. (There are other apps like strlok etc). Ohh you will need a chronograph to get best results...or atleast have an idea of your speeds

[Noisydad]

Cold dense air particularly effects slow, heavy bullets such our beloved black powder loads.
Cold winter air will make them shoot low - like 2 feet at just 200 yards (depending on the rifle).
Hot, summer air will make them fly over the target If you forget your sight settings. I’m guilty of both lol.

[TassieTiger]

Now the app while a great tool will not tell you the effect the type of powder you use will have on your groups.

How does a different powder effect groups ? Given, the app demands A velocity data point - how does a different powder affect poi?

[marksman]

pay him no attention Tassie, you know he's full of it and just baiting

[Sergeant Hartman]

I am not replying to Tassie. But marksman are you saying that that you disagree with

Ammo using alliant or vivaturi powders (anything except ADI, well reality is that even ADI changes) that is zeroed at 200m on 35deg day will shoot the same spot on a cold winters morning of 2 degrees?

Ok tassie, your question is valid, and i believe i might not explained well. Most people who shot will look at the ammo box and go say 3000fps. And likely to enter that number into their ballistics app, as no one carries a chronograph everytime they shoot. We also know is that some powders (even ADI, but to a lesser extent) can vary their speeds quite a lot based on temperature.

[in2anity]

Just shoot a damned sighter and be done with it. We get two - it's great.

[marksman]

Just shoot a damned sighter and be done with it. We get two - it's great.

simples

[brett1868]

I was probably a bit simplistic in my earlier reply. Temperature and air density are related but lets not forget altitude as having a significant effect. A good ballistic app will take into account multiple factors including the ability to list several velocities for the same cartridge based on temperature. When I compete I keep my ammo in a small esky out of the sun and extract rounds as needed so as not to give them time to cool down or heat up.

[in2anity]

I was probably a bit simplistic in my earlier reply. Temperature and air density are related but lets not forget altitude as having a significant effect. A good ballistic app will take into account multiple factors including the ability to list several velocities for the same cartridge based on temperature. When I compete I keep my ammo in a small esky out of the sun and extract rounds as needed so as not to give them time to cool down or heat up.

That's pretty hardcore What discipline is that? And what distances? Is that F-Open?

[brett1868]

I was probably a bit simplistic in my earlier reply. Temperature and air density are related but lets not forget altitude as having a significant effect. A good ballistic app will take into account multiple factors including the ability to list several velocities for the same cartridge based on temperature. When I compete I keep my ammo in a small esky out of the sun and extract rounds as needed so as not to give them time to cool down or heat up.

That's pretty hardcore What discipline is that? And what distances? Is that F-Open?

I shoot FCSA 50 Caliber comps in Australia, I'm also the current 1000 & 600yd title holder in Unlimited and Heavy gun classes. I also do alright in the 1000yd open comps placing 2nd last year. The Aus titles are being held again on the first weekend of October in Warracknabeal Vic and all going to plan I'll liberate more trophy's from the Mexicans

I've been doing a lot of practise out to 2 miles in preparation for a shot in the KOT2M comp in New Mexico next year.

[Harrynsw]

I was probably a bit simplistic in my earlier reply. Temperature and air density are related but lets not forget altitude as having a significant effect. A good ballistic app will take into account multiple factors including the ability to list several velocities for the same cartridge based on temperature. When I compete I keep my ammo in a small esky out of the sun and extract rounds as needed so as not to give them time to cool down or heat up.

That's pretty hardcore What discipline is that? And what distances? Is that F-Open?

I shoot FCSA 50 Caliber comps in Australia, I'm also the current 1000 & 600yd title holder in Unlimited and Heavy gun classes. I also do alright in the 1000yd open comps placing 2nd last year. The Aus titles are being held again on the first weekend of October in Warracknabeal Vic and all going to plan I'll liberate more trophy's from the Mexicans

I've been doing a lot of practise out to 2 miles in preparation for a shot in the KOT2M comp in New Mexico next year.

In awe of your achievements Brett. Well done.

[in2anity]

I shoot FCSA 50 Caliber comps in Australia, I'm also the current 1000 & 600yd title holder in Unlimited and Heavy gun classes. I also do alright in the 1000yd open comps placing 2nd last year. The Aus titles are being held again on the first weekend of October in Warracknabeal Vic and all going to plan I'll liberate more trophy's from the Mexicans

I've been doing a lot of practise out to 2 miles in preparation for a shot in the KOT2M comp in New Mexico next year.

Onya mate while i have your attention, do you neck-turn and FLS every reload?

[TassieTiger]

I was probably a bit simplistic in my earlier reply. Temperature and air density are related but lets not forget altitude as having a significant effect. A good ballistic app will take into account multiple factors including the ability to list several velocities for the same cartridge based on temperature. When I compete I keep my ammo in a small esky out of the sun and extract rounds as needed so as not to give them time to cool down or heat up.

That's pretty hardcore What discipline is that? And what distances? Is that F-Open?

I shoot FCSA 50 Caliber comps in Australia, I'm also the current 1000 & 600yd title holder in Unlimited and Heavy gun classes. I also do alright in the 1000yd open comps placing 2nd last year. The Aus titles are being held again on the first weekend of October in Warracknabeal Vic and all going to plan I'll liberate more trophy's from the Mexicans

I've been doing a lot of practise out to 2 miles in preparation for a shot in the KOT2M comp in New Mexico next year.

Watched a few 2 mile videos - a LOT of Maths and science behind it...Some of the firearms they use? Wow...45kgs of pure porn! Done well Brett.

[brett1868]

Onya mate while i have your attention, do you neck-turn and FLS every reload?

If you watch any of the Bryan Litz doco on YouTube from the 2017 KOT2M you might see me lurking in the background. I observed that comp then competed in the World Titles straight after which was both enjoyable and extremely frustrating.

I do neck turn and a pile of other prep work to brass that needs to hit 600yds or more as there's not much to be gained from the full prep on hunting rounds.
For the 50 I start with quality brass - Lapua, FLRS, Trim, Neck expand, Neck turn to 0.018" wall thickness, Anneal, FLRS again, Primer pocket uniform, Flash hole uniform, Seat old primer in backwards, Weigh and zero scale, Fill with water and weigh again recording the capacity in gr H2O, Remove primer, Dry, Measure case wall thickness at the midpoint, Notch the rim on the thinnest section, Prime, Charge, Seat long, Measure and adjust seating before final seat, Check and adjust concentricity depending on projectile. Store in custom made box with projectile pointed down.

Clarification -
Case mass is irrelevant as 2 cases of the same mass can have different internal capacities.
Case wall thickness @ midpoint - Long cases can banana in the chamber when fired which affects concentricity. Chambering the round in the same direction minimises variations in POI at distance.

Pic below is the full potato of prep, using 808gr LeHigh defence bore rider projectiles that I import from the U.S of A. With a light load of 217.5gr of AR2218 they produce 2600fps with a SD of 6.8 and ES of 2.7 which is friggen awesome for this cartridge. Best 5 shot group so far was 5 into 3.8" & 1000yds and it hits harder then the 308 on the right does at the muzzle

IMG_3866.jpg (314.46 KiB) Viewed 5168 times

[Aliqua]

I was probably a bit simplistic in my earlier reply. Temperature and air density are related but lets not forget altitude as having a significant effect. A good ballistic app will take into account multiple factors including the ability to list several velocities for the same cartridge based on temperature. When I compete I keep my ammo in a small esky out of the sun and extract rounds as needed so as not to give them time to cool down or heat up.

That's pretty hardcore What discipline is that? And what distances? Is that F-Open?

I shoot FCSA 50 Caliber comps in Australia, I'm also the current 1000 & 600yd title holder in Unlimited and Heavy gun classes. I also do alright in the 1000yd open comps placing 2nd last year. The Aus titles are being held again on the first weekend of October in Warracknabeal Vic and all going to plan I'll liberate more trophy's from the Mexicans

I've been doing a lot of practise out to 2 miles in preparation for a shot in the KOT2M comp in New Mexico next year.

That is simply wow! Congrats and good luck !

On a side note, I love your signature

[SCJ429]

Unbelievable ES when you are burning over 200 grains of powder. Those projectiles look the ducks guts.