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How much does temp effect velocity?

Travis Hallam
I was just wondering how much the temperature would effect the velocity of a hunting bullet. Our temperature varies greatly in North Dakota so I was wondering if I shoot my rifle at 300 yards now when it is in the 70's, will the bullet drop be significantly different when it is hunting season with temps near zero degrees.

Thanks in advance for your replies.

Mad Dog
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6 comments

Date Votes
  • pack rat633
    That depends. It seems to be determined by the powder type. Some powders are temp sensitive, some are not. Check the manufactures sites to see which ones are. I think Hodgen has the most non-sensitive powders out. I've tried to verify how much the velocity drops in cold weather here in Wyoming, but the chrony won't work in sub-freezing weather. During 100 degree weather the crony shows 10-20% velocity gains, and the cases show signs of excess presure in hot loads.

    SEMPER FI MAC, SEMPER FI
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  • Kdub
    If you load with heat sensitive powders, or shoot factory loads with such powders, yes there will be a difference in velocities. You will lose velocity in the colder extremes and gain velocity in the hotter extremes.

    An example, I live in a high heat desert area. Loads developed in the cooler winter months (50*-65*) will have higher pressures and higher velocities (generally 200 fps) when shot in the summer with 110*-115* temps. I have to remember which loads were loaded for what conditions. In the summer, the ammo is stored in a cooler at the range and only taken out when needed.

    The newer temprature insensitive powders (Hodgdons Extreme series is one)make this a moot consideration. I can load the same year 'round and not worry about it.

    Keep off the Ridgeline
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  • 1KYDSTR
    I will agree in principal with what the others have said here but want to put my vote in for VitaVouri Oy powders. The Finns have a REAL need for a series of powders that will operate from the 80 degree range all the way down to arctic circle temps. The terrain they inhabit dictates this, and the powders were developed originally with the temp extreems the Finnish military has to deal with so you can bet they did their homework!

    "When I cease learning...I'm dead"(Me)
    "Power corrupts...Absolute power corrupts absolutely"(Descartes?)
    "History is written by winners"(Patton)
    "You get a lot farther with a kind word and a gun than you do with a kind word alone!"(Al Capone)
    "There is nothing lower than the human race...except the French" (Samuel Clemens)
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  • Travis Hallam
    SO... If I am using factory 270 WSM Winchester 130 grain silver tips, how do I know if the powdwer is temp sensitive?

    How about remington in a 150 grain scirocco for a 7mm Rem mag?

    Thanks again for the replies.

    Mad Dog
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  • Kdub
    Shoot'um in hot weather and then again in cold weather and see if the POI (point of impact) changes. [;)]

    Keep off the Ridgeline
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  • Ray Boone
    When I was involved with shooting 155mm howitzers about 35 years ago, we used an extruded powder that was about the shape of 4350, but was the size of pencils cut into chunks, about 3/8" x 1". I recall we had a thermometer in the powder, in the powder bunker, and this reading was calculated into the computation for setting the guns to get the bullets to a particular location. The low temperature was about 70 degrees and the high was a very unpleasant 128 degrees. This nearly 60 degree variance in the powder temperature resulted in about a 10% adjustment in the powder to obtain the same trajectory. I'm guessing that developments in powder manufacture for small arms have allowed the affects of termperature to be minimized, or at least so it is advertised; however I'd do as suggested, shoot in both temperatures and see if they go to the same or different place.
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