Chronograph at different temps?

Forums General Discussion Chronograph at different temps?

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    BitFrost
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    Hello.

    I tested my rifle trough the chronograph this fall and landed at an average of 900fps/274mps muzzle velocity. At that time it might have been around 15degrees(celcius).
    This time of year it differs from about +3 till -25. Temperature seems to have quite a bit to say about my pellet speed as I’m now(at -10) reaching about 870fps/265mps muzzle velocity.
    The temperature from day to day swings quite a bit and my POI is not the same as it was the day before.

    Any experience with this?

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    Alan
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    Well, hot air is lighter which speaks volumes if you’ll excuse the pun!

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    aa_limited
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    what gun are you using as well the sun may or not be as bring. your chroney wil read differently in different brightness settings

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    BitFrost
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    @alan, you are excused :P
    I thought 10mps in difference was a lot when measuring muzzle velocity. I would have understood it better if I was measuring it from a distance, say a few meters or so.
    I’m using the FX Wildcat .25. The sun has been gone in north of Norway for quite some time now. I’m using my chrony with some home made lighting system. It really measures differently if the light is different? That don’t seem right to me…

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    Alan
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    I’ve never noticed that the velocity was different with any specific light source, however things like florescent lighting can interfere with the chronograph and keep it from working. But, if the shades are in place, even that issue doesn’t occur.  

    To answer your question…. In really cold weather, say -10°C, my 397 velocity hovers around 680 FPS (7.8 gr. Red Fires). During the summer months, it hovers around 700 FPS. 

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    danhor7
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    I’m working on another video at the moment that pertains more specifically to what you’re experiencing. 

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    Termocefalo
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    It’s normal that the bullet velocity slow down in cold weather , hot air it’s less dense because the particles in the air have more energy and spread.Lower density in the air result in less drag to the proyectil in external ballistic.Cold weather affects even more to fire guns due to powder combustion in internal and external ballistic too.
    Sorry for my spelling.
     

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    BitFrost
    Participant
    Member

    Thanks all for your knowledge!
    How(if you have strelok) have you guys set up Strelok?
    -Zeroing weather enabled?
    -Chronographed pellets at different temps?
    I see there is an option to put in pellet speed at different temperatures, and strelok figures out the inbetweens(?).

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    crosman2016
    Participant
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    Well, makes sense.  Hot ammo in a firearm will increase it’s velocity, so it just seems likely that hotter ambient temperature will do the same with a pellet.

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    Termocefalo
    Participant
    Member

    I set up Strelok Pro taking care about weather, altitude, speed and all the variables that this app give us, but really matters if you do long range shooting….at close distances (40 to 70 metres) doesn’t change a lot your POI, i mean with no strong wind( I do with .303 cal 50.15 gr) .At longer distances its when Strelok start to make your life easier, and works very good when you add weatherflow. 

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    John_in_Ma
    Participant
    Member

    As for your poi change it is likely the scope changing with temperature. Shoot three rounds every few minutes from the time you bring the gun out untill it reaches the outside temp. This shift should be repeatable.

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