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Cold Bore Zero...How Cold?
#6619447
01/06/17 05:17 PM
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Joined: Aug 2012
Posts: 15,570
TexFlip
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Cold bore on my rifles is typically shot above 80° at the range. This morning while freezing my azz in the stand I was wondering how colder weather could affect a cold bore shot. Barrel temp on my rifle was probably near 30°. Doesn't really matter in most hunting situations for me as I don't hunt in extreme cold but a few times a year and precision is relative when hunting. How do sub freezing temps affect cold bore shots on rifles that are zeroed in warmer weather?
Just to make sure that it is done thoroughly, I go both ways.
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Re: Cold Bore Zero...How Cold?
[Re: TexFlip]
#6619456
01/06/17 05:22 PM
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Joined: Oct 2004
Posts: 39,549
redchevy
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I don't know.
ive shot deer in the 20's at appx. 100 yards in the neck with now problem.
It's hell eatin em live
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Re: Cold Bore Zero...How Cold?
[Re: TexFlip]
#6619465
01/06/17 05:29 PM
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Joined: Dec 2008
Posts: 41,173
J.G.
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Depends on the powder in the case. Temp sensitive powders, and cold weather, can cause POI to drop, even at 100 yards. Opposite is true for heat, with temp sensitive powders, POI can raise.
When temp drops, density altitude drops, meaning the air is more dense when cold. That also can cause a POI shift low. But these shifts might only be .1 to .3 Mil, or 1/4 to 1 1/4 MOA. That's not the end of the world on near shots. If a shot on a coyote at 500 yards is a possibility, then you may very well miss if you do not know your ambient temperature zero shifts.
Fortunately for me, I get to go to a rifle range several times a week, all year. So I get to see zero shifts with weather changes, and allow for it.
800 Yard Steel Range Precision Rifle Instruction Memberships and Classes Available
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Re: Cold Bore Zero...How Cold?
[Re: J.G.]
#6619499
01/06/17 05:52 PM
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Joined: Sep 2016
Posts: 1,088
Creedmoor
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Depends on the powder in the case. Temp sensitive powders, and cold weather, can cause POI to drop, even at 100 yards. Opposite is true for heat, with temp sensitive powders, POI can raise.
Excellent answer. And just one more reason to roll your own.
. There's a fine line between BRAVE ... and STUPID.
The two most important days in your life are the day you are born and the day you find out why.
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Re: Cold Bore Zero...How Cold?
[Re: TexFlip]
#6619680
01/06/17 07:35 PM
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Joined: Aug 2009
Posts: 22,716
BigPig
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Our snipers shoot every Monday morning, regardless of the conditions so that way they know A) the clean cold bore, because they only get 1 chance 2) confirm ZERO and data log for court purposes
The difference between gun to gun is all different, that's why each sniper has his own. As far as temps go, just depends on a bunch of factors that Jason covered. They use factory Winchester Silver tip 168gr 308 in an Accuracy International rifle.
Last edited by BigPig; 01/06/17 07:37 PM.
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Re: Cold Bore Zero...How Cold?
[Re: BigPig]
#6619743
01/06/17 08:10 PM
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Joined: Dec 2008
Posts: 41,173
J.G.
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Our snipers shoot every Monday morning, regardless of the conditions so that way they know A) the clean cold bore, because they only get 1 chance 2) confirm ZERO and data log for court purposes
The difference between gun to gun is all different, that's why each sniper has his own. As far as temps go, just depends on a bunch of factors that Jason covered. They use factory Winchester Silver tip 168gr 308 in an Accuracy International rifle. And I have no doubt each sniper has a log book for that rifle. Every one of my bolt action rifles wear a stock pack. In that stock pack is the smallest spiral notebook you can get at any office supply isle. I log temp, DA, and my wind call. Then shot distance, what I applied for a correction, and the result, good or bad. I'm not a military or LE sniper, but I do want the data so that I can make that hit on hog or coyote as far out as I can see him. Around my land are wide expanses of open ground, with distant shot potential being very high. I don't want to mess up the shot, so I keep logs during practice.
800 Yard Steel Range Precision Rifle Instruction Memberships and Classes Available
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Re: Cold Bore Zero...How Cold?
[Re: TexFlip]
#6619820
01/06/17 09:01 PM
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Joined: Jul 2008
Posts: 22,260
Texas Dan
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IMO, the extreme cold is more likely to impact the accuracy of the shooter than his/her rifle. Heavy clothing extends the length of pull to the shoulder, gloves can alter finger movement on the trigger, not to mention the impact of the cold on the shooter's overall physical performance. Many a buck owes his life to a case of bucket fever combined with cold chills.
"Some people will never like you because your spirit irritates their demons."
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Re: Cold Bore Zero...How Cold?
[Re: TexFlip]
#6619892
01/06/17 09:57 PM
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Joined: Nov 2010
Posts: 29,609
SapperTitan
Taking Requests
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It's currently 23 dog where I'm hunting in Erath county. If a pig walks out I'll let ya know how much of a difference it makes haha
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Re: Cold Bore Zero...How Cold?
[Re: SapperTitan]
#6620039
01/06/17 11:13 PM
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Joined: Feb 2010
Posts: 2,289
watchale
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It's currently 23 dog where I'm hunting in Erath county. If a pig walks out I'll let ya know how much of a difference it makes haha
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Re: Cold Bore Zero...How Cold?
[Re: J.G.]
#6620265
01/07/17 12:53 AM
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Joined: May 2010
Posts: 4,073
RedSnake
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Depends on the powder in the case. Temp sensitive powders, and cold weather, can cause POI to drop, even at 100 yards. Opposite is true for heat, with temp sensitive powders, POI can raise.
When temp drops, density altitude drops, meaning the air is more dense when cold. That also can cause a POI shift low. But these shifts might only be .1 to .3 Mil, or 1/4 to 1 1/4 MOA. That's not the end of the world on near shots. If a shot on a coyote at 500 yards is a possibility, then you may very well miss if you do not know your ambient temperature zero shifts.
Fortunately for me, I get to go to a rifle range several times a week, all year. So I get to see zero shifts with weather changes, and allow for it. Hey JG -- the Shooter App has an 'enable zero atmosphere' function in the options when you are in the 'edit' screen for a given load. Supposedly if you have that enabled and input your atmospheric conditions at the time you zero with that load it will automatically adjust the calculated dope when the atmospheric conditions change. So far it has seemed very accurate. It has had me go up or down 0.1 MIL from my standard known 100 yd 0 depending on the DA.
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Re: Cold Bore Zero...How Cold?
[Re: RedSnake]
#6620336
01/07/17 01:30 AM
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Joined: Dec 2008
Posts: 41,173
J.G.
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I'm aware.
On Android it requires barometric pressure, and temp. Since my Kestrel was stolen in April, I have no way to input barometric pressure.
800 Yard Steel Range Precision Rifle Instruction Memberships and Classes Available
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Re: Cold Bore Zero...How Cold?
[Re: TexFlip]
#6621253
01/07/17 07:58 PM
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Joined: Nov 2010
Posts: 29,609
SapperTitan
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So I shot at a raccoon last night 120 yds and missed. I found it odd that I missed bc I have shot about 8 of them in the last week and not missed any of them. Went out today and verified zero and it was hitting almost 3 inches low at 100. Made an adjustment on the NV scope and was dead on. I don't think it was the cold maybe I banged the scope or something not sure why it was that far off.
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Re: Cold Bore Zero...How Cold?
[Re: TexFlip]
#6621329
01/07/17 09:06 PM
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Joined: May 2015
Posts: 4,140
Dalee7892
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Sapper, the raccoon bandits readjusted your scope. Been killing to many of their family.
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Re: Cold Bore Zero...How Cold?
[Re: Dalee7892]
#6621334
01/07/17 09:10 PM
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Joined: Nov 2010
Posts: 29,609
SapperTitan
Taking Requests
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Sapper, the raccoon bandits readjusted your scope. Been killing to many of their family. that might be the case. I've been on a raccoon killing spree. Got three more this am in the dukes.
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