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Cold air's effect on rifle trajectory?
- Thread starter zahc
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Andrew Wyatt
Member
your rifle will shoot high.
using the .243 with 80 grain preset on my bullet flight iphone app, the difference in drop at 400 yds was 1.6 inches.
using the .243 with 80 grain preset on my bullet flight iphone app, the difference in drop at 400 yds was 1.6 inches.
check out the various ballistic calculators online and you will find that air temperature has no calculated effect. Altitude does though. Temperature will effect things like propellant performance, and barrel cooling which will result in real world differences in POI
Uncle Mike
Member
Cold air>>>> Cold air is MORE DENSE than warm air, more air molecules per given space, less water molecules in that air, water molecules do not have any substantial effect on the bullet.The more air the bullet must move through, the more drag on the bullet, the bullet doesn't fly as far, or as flat.
Dense, or cold air is good for airplane wings, normally aspirated engines, but bad for bullets.
All things being equal....Hypothetically, a bullet sighted in at 100y will drop 58" on a 60 degree day but only drop 56" on a 90 degree day.
Warm air....less dense, less air molecules in a given space, more water molecules.
Less air molecules for the bullet to move through, less drag on the bullet, the bullet fly's farther and flatter.
The same can be said of barometric pressure.....HIGH barometric pressure...MORE air molecules in a given space, bullet has more air molecules to travel through, more drag on the bullet, bullet doesn't fly as far or as flat.
LOW Barometric Pressure..... LESS air molecules in a give space, bullet has less air molecules to move through, less drag on the bullet, bullet fly's farther and flatter.
Elevation.... HIGH Elevation, less Barometric pressure, LESS, air molecules per given space, LESS air molecules for the bullet to move through, less drag on bullet, bullet flys farther and flatter.
LOW Elevation.... MORE air pressure, more air molecules per given space, more air molecules for bullet to move through, more drag on bullet, bullet doesn't fly as far or as flat.
So, let's recap: Assuming you're sighted in and dead on at 100y. at a certain atmosphere, then, things change,it gets:
HOT(er)>>>> Bullet will hit HIGH(er) at 100y
COLD(er)>>>> Bullet will hit LOW(er) at 100y.
Your dead on at 100y and the Barometric Pressure:
INCREASES(High Pressure)>>>> Bullet will hit LOW(er) at 100y
DECREASES(Low Pressure)>>>> Bullet will hit HIGH(er) at 100y
Your dead on at 100y and you: (Above Sea Level)
INCREASE your Elevation>>>> Bullet will hit HIGH(er) at 100y
DECREASE your Elevation>>>> Bullet will hit LOW(er) at 100y
This meaning you, the shooter increases or decreases your elevation in regards to mean sea level, nothing to do with your sights on the firearm.
Hope this helps...Merry Christmas!
Dense, or cold air is good for airplane wings, normally aspirated engines, but bad for bullets.
All things being equal....Hypothetically, a bullet sighted in at 100y will drop 58" on a 60 degree day but only drop 56" on a 90 degree day.
Warm air....less dense, less air molecules in a given space, more water molecules.
Less air molecules for the bullet to move through, less drag on the bullet, the bullet fly's farther and flatter.
The same can be said of barometric pressure.....HIGH barometric pressure...MORE air molecules in a given space, bullet has more air molecules to travel through, more drag on the bullet, bullet doesn't fly as far or as flat.
LOW Barometric Pressure..... LESS air molecules in a give space, bullet has less air molecules to move through, less drag on the bullet, bullet fly's farther and flatter.
Elevation.... HIGH Elevation, less Barometric pressure, LESS, air molecules per given space, LESS air molecules for the bullet to move through, less drag on bullet, bullet flys farther and flatter.
LOW Elevation.... MORE air pressure, more air molecules per given space, more air molecules for bullet to move through, more drag on bullet, bullet doesn't fly as far or as flat.
So, let's recap: Assuming you're sighted in and dead on at 100y. at a certain atmosphere, then, things change,it gets:
HOT(er)>>>> Bullet will hit HIGH(er) at 100y
COLD(er)>>>> Bullet will hit LOW(er) at 100y.
Your dead on at 100y and the Barometric Pressure:
INCREASES(High Pressure)>>>> Bullet will hit LOW(er) at 100y
DECREASES(Low Pressure)>>>> Bullet will hit HIGH(er) at 100y
Your dead on at 100y and you: (Above Sea Level)
INCREASE your Elevation>>>> Bullet will hit HIGH(er) at 100y
DECREASE your Elevation>>>> Bullet will hit LOW(er) at 100y
This meaning you, the shooter increases or decreases your elevation in regards to mean sea level, nothing to do with your sights on the firearm.
Hope this helps...Merry Christmas!
Last edited:
It isn't so much the trajectory, but the accuracy you have to worry about. You know, from the bullet shivering and all ... *groan* I know. I couldn't help myself.
On a serious note, what's great about this site is not only can you get answers, as seen, but fleshed out explanations as well.
On a serious note, what's great about this site is not only can you get answers, as seen, but fleshed out explanations as well.
rangerruck
Member
...was gonna say something, but after unky mike, nothing left to be said!
Uncle Mike
Member
Well, some folks may need to see the 'under belly' to understand it all! lol hehehehe
How'd I do...? hehehehehe
Just like flying, sometimes the answer is simple, but complicated!
How'd I do...? hehehehehe
Just like flying, sometimes the answer is simple, but complicated!
Steve Marshall
Member
It's a complicated thing. But assume a 100 yard zero(yeah, I know you shot at 400). At 35 degrees your bullet will drop 37.75". At 100 degrees, your bullet will drop 35.78". This, assuming a Sierra spitzer boat tail at 2600 FPS. The problem is that your zero will likely change also, so you'd have to rezero. But the net effect is about 2" from a 100 yard zero.
Wind Speed Altitude Clicks/MOA Sight Height Max Range Range Interval Sectional Density Muzzle Velocity Bullet Weight Ballistic Coefficient Temperature Zero Range Ballistics Calculator
Temp: 59
Muzzle -1.5 Infinity 3000 3597 77.14 0.000 0.0 NaN 1312
25 -0.1 1 2943 3462 75.68 0.025 0.0 1 1239
50 1.1 -8 2887 3330 74.23 0.051 0.2 1 1169
75 2.0 -10 2831 3203 72.80 0.077 0.4 2 1103
100 2.6 -10 2776 3080 71.39 0.104 0.7 3 1040
125 2.9 -9 2722 2961 70.00 0.131 1.1 3 980
150 3.0 -8 2669 2846 68.62 0.159 1.6 4 924
175 2.7 -6 2616 2735 67.26 0.188 2.2 5 870
200 2.1 -4 2564 2627 65.92 0.217 2.9 6 819
225 1.2 -2 2512 2522 64.60 0.246 3.7 6 771
250 0.0 0 2461 2421 63.29 0.276 4.6 7 725
275 -1.6 2 2411 2324 62.00 0.307 5.6 8 681
300 -3.6 5 2362 2229 60.73 0.338 6.8 9 640
325 -6.0 7 2313 2138 59.47 0.371 8.0 9 601
350 -8.7 10 2265 2050 58.23 0.403 9.4 10 564
375 -11.9 12 2217 1964 57.01 0.437 10.9 11 529
400 -15.6 15 2170 1881 55.79 0.471 12.5 12 496
425 -19.7 18 2123 1801 54.58 0.506 14.3 13 465
450 -24.3 21 2076 1723 53.39 0.542 16.1 14 435
475 -29.4 24 2031 1648 52.22 0.578 18.2 15 407
500 -35.0 27 1986 1576 51.06 0.616 20.4 16
Temp: 0
Range
yds Path
in ComeUp
clicks Velocity
fps Energy
ft/lbs Momentum
lb ft/s ToF
sec Windage
in Windage
clicks Optimal
Game Wgt
Muzzle -1.5 Infinity 3000 3597 77.14 0.000 0.0 NaN 1312
25 -0.1 1 2943 3462 75.68 0.025 0.0 1 1239
50 1.1 -8 2887 3330 74.23 0.051 0.2 1 1169
75 2.0 -10 2831 3203 72.80 0.077 0.4 2 1103
100 2.6 -10 2776 3080 71.39 0.104 0.7 3 1040
125 2.9 -9 2722 2961 70.00 0.131 1.1 3 980
150 3.0 -8 2669 2846 68.62 0.159 1.6 4 924
175 2.7 -6 2616 2735 67.26 0.188 2.2 5 870
200 2.1 -4 2564 2627 65.92 0.217 2.9 6 819
225 1.2 -2 2512 2522 64.60 0.246 3.7 6 771
250 0.0 0 2461 2421 63.29 0.276 4.6 7 725
275 -1.6 2 2411 2324 62.00 0.307 5.6 8 681
300 -3.6 5 2362 2229 60.73 0.338 6.8 9 640
325 -6.0 7 2313 2138 59.47 0.371 8.0 9 601
350 -8.7 10 2265 2050 58.23 0.403 9.4 10 564
375 -11.9 12 2217 1964 57.01 0.437 10.9 11 529
400 -15.6 15 2170 1881 55.79 0.471 12.5 12 496
425 -19.7 18 2123 1801 54.58 0.506 14.3 13 465
450 -24.3 21 2076 1723 53.39 0.542 16.1 14 435
475 -29.4 24 2031 1648 52.22 0.578 18.2 15 407
500 -35.0 27 1986 1576 51.06 0.616 20.4 16 380
All else kept the same. Drop is the same with a 60 degree difference. Ballistically speaking there will be no difference. Again propellant performance may change in the real world effecting the speed (notice I didn't use the word "velocity") of the bullet. The calculator doesn't know that because I kept speed constant.
Temp: 59
Muzzle -1.5 Infinity 3000 3597 77.14 0.000 0.0 NaN 1312
25 -0.1 1 2943 3462 75.68 0.025 0.0 1 1239
50 1.1 -8 2887 3330 74.23 0.051 0.2 1 1169
75 2.0 -10 2831 3203 72.80 0.077 0.4 2 1103
100 2.6 -10 2776 3080 71.39 0.104 0.7 3 1040
125 2.9 -9 2722 2961 70.00 0.131 1.1 3 980
150 3.0 -8 2669 2846 68.62 0.159 1.6 4 924
175 2.7 -6 2616 2735 67.26 0.188 2.2 5 870
200 2.1 -4 2564 2627 65.92 0.217 2.9 6 819
225 1.2 -2 2512 2522 64.60 0.246 3.7 6 771
250 0.0 0 2461 2421 63.29 0.276 4.6 7 725
275 -1.6 2 2411 2324 62.00 0.307 5.6 8 681
300 -3.6 5 2362 2229 60.73 0.338 6.8 9 640
325 -6.0 7 2313 2138 59.47 0.371 8.0 9 601
350 -8.7 10 2265 2050 58.23 0.403 9.4 10 564
375 -11.9 12 2217 1964 57.01 0.437 10.9 11 529
400 -15.6 15 2170 1881 55.79 0.471 12.5 12 496
425 -19.7 18 2123 1801 54.58 0.506 14.3 13 465
450 -24.3 21 2076 1723 53.39 0.542 16.1 14 435
475 -29.4 24 2031 1648 52.22 0.578 18.2 15 407
500 -35.0 27 1986 1576 51.06 0.616 20.4 16
Temp: 0
Range
yds Path
in ComeUp
clicks Velocity
fps Energy
ft/lbs Momentum
lb ft/s ToF
sec Windage
in Windage
clicks Optimal
Game Wgt
Muzzle -1.5 Infinity 3000 3597 77.14 0.000 0.0 NaN 1312
25 -0.1 1 2943 3462 75.68 0.025 0.0 1 1239
50 1.1 -8 2887 3330 74.23 0.051 0.2 1 1169
75 2.0 -10 2831 3203 72.80 0.077 0.4 2 1103
100 2.6 -10 2776 3080 71.39 0.104 0.7 3 1040
125 2.9 -9 2722 2961 70.00 0.131 1.1 3 980
150 3.0 -8 2669 2846 68.62 0.159 1.6 4 924
175 2.7 -6 2616 2735 67.26 0.188 2.2 5 870
200 2.1 -4 2564 2627 65.92 0.217 2.9 6 819
225 1.2 -2 2512 2522 64.60 0.246 3.7 6 771
250 0.0 0 2461 2421 63.29 0.276 4.6 7 725
275 -1.6 2 2411 2324 62.00 0.307 5.6 8 681
300 -3.6 5 2362 2229 60.73 0.338 6.8 9 640
325 -6.0 7 2313 2138 59.47 0.371 8.0 9 601
350 -8.7 10 2265 2050 58.23 0.403 9.4 10 564
375 -11.9 12 2217 1964 57.01 0.437 10.9 11 529
400 -15.6 15 2170 1881 55.79 0.471 12.5 12 496
425 -19.7 18 2123 1801 54.58 0.506 14.3 13 465
450 -24.3 21 2076 1723 53.39 0.542 16.1 14 435
475 -29.4 24 2031 1648 52.22 0.578 18.2 15 407
500 -35.0 27 1986 1576 51.06 0.616 20.4 16 380
All else kept the same. Drop is the same with a 60 degree difference. Ballistically speaking there will be no difference. Again propellant performance may change in the real world effecting the speed (notice I didn't use the word "velocity") of the bullet. The calculator doesn't know that because I kept speed constant.
Uncle Mike
Member
All else kept the same. Drop is the same with a 60 degree difference. Ballistically speaking there will be no difference.
Something's wrong......
Uncle Mike
Member
Right...the POI will be HIGHER in the warmer air(summer).
IF you sighted in during cooler air.
As to how much, only you can supply the needed info. to answer that question, capt.sharpshooter! lol hehehe
The difference will increase the longer the range. No, the difference isn't going to be astronomical, but there is a difference. It CAN be a bunch, when all the factors come into alignment at once.
IF you sighted in during cooler air.
As to how much, only you can supply the needed info. to answer that question, capt.sharpshooter! lol hehehe
The difference will increase the longer the range. No, the difference isn't going to be astronomical, but there is a difference. It CAN be a bunch, when all the factors come into alignment at once.
Density of the air is not solely reliant on Temperature among ambient variables. Density = Pressure/R(gas constant)X Temperature.
Stating that temperature alone will cause a certain definite change in trajectory assumes that atmospheric pressure will be constant, which as we all know may not be the case. My guess is that is why some ballistic calculators show no change based on temperature alone.
Stating that temperature alone will cause a certain definite change in trajectory assumes that atmospheric pressure will be constant, which as we all know may not be the case. My guess is that is why some ballistic calculators show no change based on temperature alone.
Uncle Mike
Member
Exactly!
Peter M. Eick
Member
Also, one must take into account that most ammo will shoot slower in colder weather. This varies from a bit to a lot depending on a bunch of things. Not the least of which is the powder.
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