Cold weather velocity

Discussion in 'Reloading' started by Thumb hole, Dec 9, 2012.

  1. Thumb hole

    Thumb hole New Member

    Messages:
    4
    Joined:
    Dec 9, 2012
    What differences do you notice in velocities between cold weather shooting and warm weather shooting
     
  2. Lefty7mmstw

    Lefty7mmstw Well-Known Member

    Messages:
    4,280
    Joined:
    May 13, 2012
    It really depends on the combo, but 50-100 fps is to be expected. I've seen that spread with Imr, H, and RL. I don't burn much ball powder, but that can sometimes be a bit worse.
     

  3. Frank in the Laurels

    Frank in the Laurels Well-Known Member

    Messages:
    659
    Joined:
    Jul 15, 2007
    The type of powder your working with has more to do with it than anything else...shoot some ball powders in the hot summer and then shoot them at zero degrees!!!! You'll be stunned !!! I always try to work up hunting loads with any of the H-series extreme powders, there might be some difference but for the most part I hardly think lung tissue or heart valves will hardly notice.....
     
  4. Greyfox

    Greyfox Well-Known Member

    Messages:
    3,689
    Joined:
    Jan 21, 2008
    I have found very little in the way of velocity differences using the Hogdon Exteme powders, particularly Retumbo in my 6.5x284. I have shot this powder between 0 and 85 degrees with no appreciable difference in velocities, or POI. I do make the ballistic drop adjustments for the temperature change though.
     
  5. rooster721

    rooster721 Well-Known Member

    Messages:
    196
    Joined:
    Jan 6, 2012
    Greyfox is right.

    I'm up in Alberta, Canada and shoot in temps ranging from say -15F to also high 80's during summer months.. in fact just this past saturday was out doing some shooting, about -5F (-20C) using the Hodgdon powders.. my Muzzle velocity changes literally nothing, but the rate in which the air-density slows the bullet downrange becomes pretty obvious. Those that say one click (+/-) per 20 degrees, they're pretty close. I find a click, click n a half difference per 20 with my rifles... seems very true

    We shot to 820 this last weekend.. 440, 650 and 820 were where I set the gongs. The trajectories in one rifle using H-1000 and one using retumbo both were consistent with the 1 click per 20 statement, charts were adjusted only for temp.. no muzzle velocity adjustment what-so-ever. Good stable powder is a must**

    All that said.. I like IMR 7828 actually, as a next best to the Extreme line from Hodgdon... BUT have clocked ~100fps swings using that 7828. Good podwer, but not for long-distances where cold/hot drastic swings take place... fwiw
     
  6. Lefty7mmstw

    Lefty7mmstw Well-Known Member

    Messages:
    4,280
    Joined:
    May 13, 2012
    also remember that not all H powders are the same. Some of the older ones like H 4895 even though "extreme" will vary quite a bit; I've seen 100 fps with H 4985 between cold and hot. Some of the newer ones are better I'm sure, but I use rl more so I really don't have good data on what North Dakota does to H powders.
     
  7. barnesuser28

    barnesuser28 Well-Known Member

    Messages:
    2,808
    Joined:
    Mar 2, 2012
    Lefty, i can try to get some of that info on some retumbo in a 338 Lapua and h4831 in a 25-06.
     
  8. Thumb hole

    Thumb hole New Member

    Messages:
    4
    Joined:
    Dec 9, 2012
    Thanks for getting back to me on this matter all very interesting I wonder if you guys have ever tried IMR 4831 that's the power I'm using I'm finding up to 100 ft./s difference
     
  9. Lefty7mmstw

    Lefty7mmstw Well-Known Member

    Messages:
    4,280
    Joined:
    May 13, 2012
    I'd say you are ballpark on that one.. usually a bit less but your data isn't unusual
     
  10. Thumb hole

    Thumb hole New Member

    Messages:
    4
    Joined:
    Dec 9, 2012
    Thanks for getting back to me on that I find that it's up to two clicks out at 500 yards for every hundred yards beyond that at -5 or below weather