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Old January 8, 2019, 06:34 AM   #1
Poconolg
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Barrel Temp

We all know that we should let a barrel cool off when shooting groups. On the other hand what effect does a very cold barrel have? Yesterday here in NE PA it was in the low 20's and after shooting my 5 shot group with a 22-250 thru a Lilja barrel the barrel cooled very fast. After 15 minutes it was ice cold to the touch. I had a good day shooting: 8 5 shot groups with 3 of them under 3/8".
One of them was .28". Just wondering if anyone has noticed the effect of a ice cold barrel on accuracy.
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Old January 8, 2019, 08:02 AM   #2
NoSecondBest
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Some powders are powder sensitive also. Changing temps to an extreme can have several factors contribute to group size changing. Yes, barrel temp being constant helps get better groups. Some guys actually use cooling rods in some guns to achieve this result.
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Old January 8, 2019, 08:24 AM   #3
cw308
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I never shoot in weather that cold , getting soft in my older age I guess . Use temperature label on the barrel for heat . I do find even the other way at certain temperatures the groups tighten , both powder sensitivity and barrel temperature effects group size . Sorry hard core I couldn't help I just shake to much in the cold to test .
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Old January 8, 2019, 08:55 AM   #4
Rimfire5
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I find that really cold barrels and hot barrels do effect POI on some of my most accurate rifles.
Seems that I get my best accuracy with barrel temps between 70 and under 120 degrees.
I mounted temperature strips on all of my target barrels so I know how fast the barrel temp is rising.
On cold days in the 20s, I can shoot 10 to 12 rounds before the barrel strip reads 120 degrees. When it is in the low 90s, I can shoot 5.
I let the barrel cool when it gets close to 120 degrees because I find that the POI is dropping about 1/4 inch as it reaches 120 degrees.
When you can shoot 0.28 groups like you do, a drop of 0.25 can double your group size.

The temp strips aren't calibrated so the numbers I reference here may not be the actual core barrel temperature, but the temp strip readings appear to be consistent and that is good enough to let me know when to let the barrel cool. I got the strips 10 for $12 from Amazon (I use the 86 to 140 deg. F. versions).

I agree with NoSecondBest that powders are also temperature sensitive, but if the bullets sitting are on the bench, the powder temperature doesn't change enough while you are shooting a group so the group size will not be effected. Outside temperature normally changes only a few degrees per hour during stable weather conditions in Northern VA, unless, of course, a front comes through.

However, temperature will change velocity by from 1.2 to 1.7 fps per deg. F. depending upon the powder. Aberdeen Proving Grounds did a study of .308 powder with extreme temperature variations. The biggest impact most will notice would be if you test a load in the early fall at 70 degrees and you go hunting in 20 degree temps on a late fall morning. That kind of temperature change could create a significant change in velocity, perhaps 60 to 85 fps for that kind of temperature difference depending upon powder sensitivity.

A deer wouldn't notice the difference but a bullet's POI might drop a bit lower than you had experienced during the summer.
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Old January 8, 2019, 09:34 AM   #5
30Cal
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I find it's harder to shoot well when it's really cold.
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Old January 8, 2019, 09:38 AM   #6
Unclenick
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There are several factors at work. Hot chambers pass heat very rapidly to the case and through, to the primer and the powder grains lying against the surface. Denton Bramwell did some tests suggesting barrel heat was a much bigger factor than the ambient temperature you keep the cartridges in.

Other factors include that the speed of sound in the steel that affects pressure wave timing will change with temperature and so will friction between the bullet and steel. Finally, if you have a barrel that was not stress-relieved before contouring (common in high volume production barrels), you may have asymmetrical stresses in the barrel that will change POI as the barrel temperature changes.
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Old January 8, 2019, 02:45 PM   #7
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I don't see it as an issue most days.

Enough long strings and I do see the POI walk a bit, but not dramatic jumps

I to shoot a fair amount in the 10+ deg arena, fact of life up here if you don't no winter shooting to speak of (we do have over head heaters but its an open shed so more the shooter gets benefit)

This last trip I notice first dead cold shot was up and to the right a bit (half an inch) but only if it had cooled all the way down.
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Old January 8, 2019, 02:48 PM   #8
RC20
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Quote:
I find it's harder to shoot well when it's really cold.
Hmmmm.
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Old January 8, 2019, 04:03 PM   #9
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A cold forged or cryogenically stabilized barrel will change very little. The amount of time a cartridge remains in a warm barrel will have a greater effect on grouping if the powder in that cartridge is not temperature stable.

I recently tested this with a hunting rifle at 100 yards. The rifle has guaranteed sub moa accuracy. I shot 3 rounds quickly and they grouped within the guarantee. I let the barrel cool and then shot 5 rounds at a slow rate and the group opened up on the last 3 shots. After letting the barrel cool again I shot 5 rounds but I did not put the cartridge in the chamber until I was ready to shoot. The groups returned to sub moa.

While this test isn't very scientific it has me convinced that accuracy can be affected by the temperature of the powder in the case if the rifle barrel steel was stabilized during production. Today, most all good barrels are stabilized through some means.
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Old January 8, 2019, 04:56 PM   #10
Mobuck
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My hunting and EDC rifles live outside. Regardless of temp I expect them to make a cold bore shot. Ammo is likely more affected by extreme cold than rifle barrels.
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Old January 8, 2019, 06:44 PM   #11
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Hunting and EDC are separate from Target. Good to know if they go off tangent after the first shot (EDC and not likely or enough to be an issue)

Target shooting (all I do now) I try to maintain as uniform barrel temp as I can and pace the shots so that the cartridge does not sit in a hot barrel for a long time.
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Old January 8, 2019, 09:56 PM   #12
Doyle
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If it is that cold, I'll be shivering so badly that there is no way I'd get decent groups - no matter how good the rifle is.
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Old January 9, 2019, 07:51 AM   #13
Mobuck
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"here in NE PA it was in the low 20's"

That's not really "cold", more of a "chilly". Minus 20 is "cold".
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