Cold

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Wlfdg, Oct 13, 2008.

  1. Wlfdg

    Wlfdg Well-Known Member

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    What effect should I expect the sudden onset of winter to have on my POI in my 7RM? The temp has dropped as much as 60 F.
     
  2. James Jones

    James Jones Well-Known Member

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    If the gun is bedded properly and their is suffecient relief around the barrel to allow for a little movement in the wood from the temp and humidity change (assuming its wood) their should be no differance in the weapon.

    BUT , some factory ammo will have some changes with big temp swings as will some handloaded ammo depending on the powder and primers used.

    I have put my loaded ammo in the freezer to check the differances in velocity and such before going on a hunt up north as our winters rarely get to the freezing point for more than a few hrs at a time so if i make my ammo and shoot it and all is well at 50 deg then go to Alberta and its -10 then i want to know what the rifle is gonna do their , reguardless I always shoot once at the camp to make sure everything is working correctly.

    another thing you may want to thing about is the oil or greese used to lube the internals , some of that stuff will freeze down close to zero degrees.
     

  3. Wlfdg

    Wlfdg Well-Known Member

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    I've dried up my action. I'm shooting a Vanguard,synthetic stock, Winchester Ballistic Silvertips 150gr.
     
  4. SlyOneMrGrinch

    SlyOneMrGrinch Member

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    According to the Army field manual 23-10:

    "The higher the temperature, the less dense the air. If the shooter zeros at 60 degrees F and he fires at 80 degrees, the air is leas dense, thereby causing an increase in muzzle velocity and higher point of impact. A 20-degree change equals a one-minute elevation change in the strike of the bullet."​
     
  5. Wlfdg

    Wlfdg Well-Known Member

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    Thanks. So I was right on.

    I increased my elevation by 2 MOA figuring the temp could increase as the day went on.
     
  6. jmden

    jmden Well-Known Member

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    Shoot it in the temps you will be hunting at at the distances you will be hunting at. There's no other way to know for sure what will happen. Too many variables. Typically, you'll lose some velocity which would likely cause a lower POI. But, I wouldn't generalize the situation. Shoot it and find out what it's doing before you shoot at a critter. JMHO. Good luck hunting.
     
  7. phorwath

    phorwath Well-Known Member

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    I would agree. The greater the range, the more important to shoot the rifle to check POI before shooting at the game.
     
  8. Wlfdg

    Wlfdg Well-Known Member

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    Looks like it is going to warm up again.

    In your educated opinions what distance should I limit myself to under ideal conditions if I've consistently shot comfortably out to 600yds?
     
  9. James Jones

    James Jones Well-Known Member

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    That depends on alot , what bullets are you shooting and at what speed.

    what are you shooting at?

    120gr Ballistic tip , 400yds on deer , don't shoot at elk with it

    160gr accubond , 800yds on elk or deer

    How far have you shot with that rig with confidence ,I've seen guys shoot to 300yds and make a half assed drop chart acording to some poor ballistics calculator and expect to make good hits out to 1000yds , it just don't work that way
     
  10. Wlfdg

    Wlfdg Well-Known Member

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    Absolute confidence,

    Perfect conditions; 600 yds. on paper.

    Less than ideal conditions; winds 25 mph, gusts to 45mph 45-50% value- 300 yds.

    Both with 150 gr. Ballistic Silvertips.

    I know they destroy tissue but they shoot ragged one hole groups of 4-5 rds. at 100 yds. out of my 7RM and they group 4 in a nickel at 200 yds.
     
  11. davewilson

    davewilson Well-Known Member

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    i have some experience in cold weather, down to 40-45 below. what i've seen with quite a few guns is a change in POI. it's not the ammo, but the gun. my brother had a custom that would change 6" when the temps got down to around zero.yes that's at 100 yds. the culpert is usually the stock. like that vangard you're talking about. you have a floated barrel till it gets chilly and that stock will come up and push on the barrel much harder than you could imagine. this is why some stocks cost $79 and good ones are at least 300. someone suggested putting the ammo in the freezer and i agrre with that. i recommended to all the hunters coming to Saskatchewan to also put the gun in there and shoot them when they were cold. this will tell you 2 things. #1 if the POI will change and #2 if the gun will make the ammo go off. i've heard my fair share of clicks when the temps were around zero. just because your gun is dry doesn't guarantee it'll go off when it's -20. have you ever had the bolt taken completely apart and cleaned? that's where the problem will come from. most guns come from the factory with enough greese to lubricate a wagon wheel. i'm with everyone else. the only way to know for sure is to get em cool, and shoot em over a chrono or at some distance.
     
  12. Wlfdg

    Wlfdg Well-Known Member

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    Yes, of course.
     
  13. royinidaho

    royinidaho Writers Guild

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    In a 270 Win a 58.5 gr load of RL-22 behind a 140 class bullet droped 130 FPS from 60* temps to teens. It turns out that the Chrony was/is temperature sensitive way more than the powder is.

    Thus I don't worry so much about the temp drop but I do compensate a bit for it. Its one of those last minute "fudge" things. If I 'feel' its needed. Works for me:rolleyes:

    Considering the bullet you are using, I'd stick with the 600 yard limit, as indicated by your 300 yd worse condition comment. The idea is to slay the elk.;)

    For WIW I switched from 150 Ballistic Tips to 140 NABs in my 270 AM because of the better bullet construction. Both have the same BC but I get another 100 FPS out of the 140.

    Both bullets shoot exceptionally well in the rifle.

    My thinkin' is that I'll get just a schosie bit better chance of complete penetration w/the NAB. However, I shot a Muley buck w/a 130 BT that went through 30" of deer with nearly perfect performance.

    Also, I want to attempt one of those high shoulder shots one of these times, especially in one particular spot that I hunt. DRT would mean way less work.

    BTW, how far are you from Dirk Parkinson's farm up at the end of Hog Hollow road?

    It's great chuck shooting across the old Teton Dam spot. Though there seem to be only a few chucks.
     
  14. Wlfdg

    Wlfdg Well-Known Member

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    Up in Ashton. Not to far. Less than hour. I don't know the farm but I do know the road. North Teton Creek? I was hoping to get permission to hunt a farm up that way that I was told was overrun with whitetails.I have a 1095 controlled hunt tag, whitetail doe only. Heard there were a lot of yotes too.

    I saw one chuck this whole spring. I think, like the hare, this winter really took a toll on them.