close
Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Hunting > Long Range Hunting & Shooting

Long Range Hunting & Shooting Nightforce Optics

Reply

how much does sun heated loads affect pressure?

LinkBack Thread Tools Display Modes
  #1  
Unread 09-30-2012, 10:27 AM
Silver Member
 
Join Date: Feb 2008
Location: Star, ID
Posts: 341
how much does sun heated loads affect pressure?

I shot very well yesterday including groups of 1.0" at 400(only 2 shots), 3.5"at 500, and 3.8" at 600 for 4 shots. I left my ammo in the sun on one of the 1200+ yard round trips to check targets and they went from 75deg to 101deg. Group went up to 5.5" and cases were sticky, when they had not been before.

Seems I have been fairly consistent with this gun and load at .6 to. 8moa from 200 to 600 this summer but when the temps rise groups can be up to 1.25moa. I don't feel its always me.

Seems to also cause POI change to.

So how much do you think over-heated ammo can affect groups and/or POI? PS This not a custom rifle, just an A-bolt with BOSS with an after market trigger and medalist stock.
Reply With Quote
  •   #2  
    Unread 09-30-2012, 10:45 AM
    Platinum Member
     
    Join Date: Jan 2004
    Location: Blackfoot, Idaho
    Posts: 8,859
    Re: how much does sun heated loads affect pressure?

    The evidence of what sun heated cartridges was proven pretty well by what you did.

    Long story short, it makes one helluva difference. And should be avoided at all costs.

    Direct sun light can heat an object to well over 130*. I've tested it w/an infrared thermometer.
    __________________
    I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!
    Reply With Quote

      #3  
    Unread 09-30-2012, 11:10 AM
    Platinum Member
     
    Join Date: Jan 2008
    Location: Falls Church, VA
    Posts: 3,474
    Re: how much does sun heated loads affect pressure?

    Totally agree with Roy.

    Another consideration is the powder you are using. If you are using any of the Reloder powders, they are notoriously temp sensitive, whereas the Hodgdon 'Extreme' powders are far less temp sensitive.
    __________________
    I'm not gonna shoot here. I'm gonna shoot waaaaaaaay over there!
    Reply With Quote
      #4  
    Unread 09-30-2012, 11:35 AM
    Silver Member
     
    Join Date: Feb 2008
    Location: Star, ID
    Posts: 341
    Re: how much does sun heated loads affect pressure?

    I use RL19. Tried some hogden loads but cant replicate the low teen ES I have now. Seems it starts to make a diff at 80 degrees.

    So while hunting where do you carry ammo?
    Reply With Quote
      #5  
    Unread 09-30-2012, 12:10 PM
    Platinum Member
     
    Join Date: Jan 2008
    Location: Falls Church, VA
    Posts: 3,474
    Re: how much does sun heated loads affect pressure?

    Quote:
    Originally Posted by bkondeff View Post
    I use RL19. Tried some hogden loads but cant replicate the low teen ES I have now. Seems it starts to make a diff at 80 degrees.

    So while hunting where do you carry ammo?
    RL19 might provide a good ES, but with it's temp sensitivity, ES doesn't mean much.

    I carry ammo where temp can remain stable. Generally an inside pocket.
    __________________
    I'm not gonna shoot here. I'm gonna shoot waaaaaaaay over there!
    Reply With Quote
      #6  
    Unread 09-30-2012, 01:31 PM
    Platinum Member
     
    Join Date: Jul 2004
    Location: Texas
    Posts: 7,001
    Re: how much does sun heated loads affect pressure?

    101o will/can effect the velocity a load if it was worked up at ambient temps, but when you leave them in the sun they can get much hotter and will definitely have an effect on zeros and groups.

    If you have near or max loads you can experance blown primers and stuck cases if the ammo
    in allowed to roast in the sun

    The only time I have placed my ammo in direct sunlight was when temps were very low.
    or I just kept the ammo in my pocket.

    J E CUSTOM
    __________________
    "PRESS ON"
    Reply With Quote
    Reply

    Bookmarks

    Thread Tools
    Display Modes


    Similar Threads for: how much does sun heated loads affect pressure?
    Thread Thread Starter Forum Replies Last Post
    Temperature and humidity factor - how do they affect my loads? elkfirst Reloading 23 09-16-2015 03:11 PM
    .300 RUM loads, pressure signs? 300 Rem Rifles, Bullets, Barrels & Ballistics 4 04-25-2011 02:09 PM
    Barrel twist rate's affect on pressure airstream Rifles, Bullets, Barrels & Ballistics 9 03-04-2011 09:20 PM
    New crown affect on loads Preda8or Reloading 7 06-19-2006 07:18 PM
    High Pressure Loads in 700 LA Big-un Rifles, Bullets, Barrels & Ballistics 9 03-22-2006 09:54 AM


    All times are GMT -5. The time now is 05:35 PM.


    Powered by vBulletin ©2000 - 2017, Jelsoft Enterprises Ltd.
    Content Management Powered by vBadvanced CMPS
    All content ©2010-2015 Long Range Hunting, LLC