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#6619447 - 01/06/17 11:17 AM Cold Bore Zero...How Cold?
TexFlip Online   content
THF Trophy Hunter

Registered: 08/18/12
Posts: 9988
Loc: Chambers County
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?

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#6619456 - 01/06/17 11:22 AM Re: Cold Bore Zero...How Cold? [Re: TexFlip]
redchevy Online   content
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Registered: 10/25/04
Posts: 26294
Loc: Texas
I don't know.

ive shot deer in the 20's at appx. 100 yards in the neck with now problem.
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#6619465 - 01/06/17 11:29 AM Re: Cold Bore Zero...How Cold? [Re: TexFlip]
FiremanJG Online   content
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Registered: 12/16/08
Posts: 21783
Loc: Wolfe City, TX
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.
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#6619499 - 01/06/17 11:52 AM Re: Cold Bore Zero...How Cold? [Re: FiremanJG]
Creedmoor Offline
Pro Tracker

Registered: 09/12/16
Posts: 1086
Originally Posted By: FiremanJG
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.
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#6619680 - 01/06/17 01:35 PM Re: Cold Bore Zero...How Cold? [Re: TexFlip]
BigPig Online   content
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Registered: 08/27/09
Posts: 10835
Loc: Forney, Tx
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.


Edited by BigPig (01/06/17 01:37 PM)
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#6619743 - 01/06/17 02:10 PM Re: Cold Bore Zero...How Cold? [Re: BigPig]
FiremanJG Online   content
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Registered: 12/16/08
Posts: 21783
Loc: Wolfe City, TX
Originally Posted By: BigPig
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.
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#6619820 - 01/06/17 03:01 PM Re: Cold Bore Zero...How Cold? [Re: TexFlip]
Texas Dan Offline
THF Celebrity

Registered: 07/28/08
Posts: 12350
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.
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#6619892 - 01/06/17 03:57 PM Re: Cold Bore Zero...How Cold? [Re: TexFlip]
SapperTitan Online   content
Taking Requests

Registered: 11/17/10
Posts: 22610
Loc: Killeen/Ft Hood, TX
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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#6620039 - 01/06/17 05:13 PM Re: Cold Bore Zero...How Cold? [Re: SapperTitan]
watchale Offline
Pro Tracker

Registered: 02/18/10
Posts: 1933
Loc: Tx
Originally Posted By: SapperTitan
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

rofl
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#6620265 - 01/06/17 06:53 PM Re: Cold Bore Zero...How Cold? [Re: FiremanJG]
RedSnake Online   content
Veteran Tracker

Registered: 05/08/10
Posts: 3307
Loc: Dallas / Nolan County
Originally Posted By: FiremanJG
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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#6620336 - 01/06/17 07:30 PM Re: Cold Bore Zero...How Cold? [Re: RedSnake]
FiremanJG Online   content
THF Celebrity

Registered: 12/16/08
Posts: 21783
Loc: Wolfe City, TX
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.
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#6621253 - 01/07/17 01:58 PM Re: Cold Bore Zero...How Cold? [Re: TexFlip]
SapperTitan Online   content
Taking Requests

Registered: 11/17/10
Posts: 22610
Loc: Killeen/Ft Hood, TX
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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#6621329 - 01/07/17 03:06 PM Re: Cold Bore Zero...How Cold? [Re: TexFlip]
Dalee7892 Offline
Pro Tracker

Registered: 05/04/15
Posts: 1776
Loc: Denton County
Sapper, the raccoon bandits readjusted your scope. Been killing to many of their family.

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#6621334 - 01/07/17 03:10 PM Re: Cold Bore Zero...How Cold? [Re: Dalee7892]
SapperTitan Online   content
Taking Requests

Registered: 11/17/10
Posts: 22610
Loc: Killeen/Ft Hood, TX
Originally Posted By: Dalee7892
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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