how do you measure barrel temperature in a reliable manner?

nealm66

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They probably reset the neck size which definitely helps. Not sure why they all seem to have them so dang tight to start. Well, I wish I’d never heard about it either because it’s a pita and a waist of precious components. I’ll measure new brass and if it’s close I’ll roll with it but if it’s loose, well, it’s going to be off a bit if it’s not fire formed.
 

davidu

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I have a practical application for this, trying to become very consistent at long range shooting. In the beginning at least for me, there are numerous variables to figure out, trigger pull, cheek weld, stock support, breathing, etc, etc. as well as coal, powder charge, etc. etc. When I go to the range, I have to shoot more than 5 rounds to practice or I'll be at least 200 years old before I learn to shoot. One of my rifles 308, has a lightweight barrel and it heats up considerably after 5-10 rounds. Being new, I am always wondering if I'm losing my ability to shoot or the slight expansion of the barrel diameter is affecting the groups. Once I learn how to shoot, I agree it's probably not that important. Thanks.
I use temp sensors made for rifle barrels. Easy to apply
Prairie dog hunt and it’s easy to get a barrel hot without realizing it.
They are called Bar-L temp strips
 
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Bravo 4

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Professor,
I’m going to make a suggestion that may sound as if I’m flaming you, when realistically I’m trying to just be helpful. Reading your posts in just this thread alone makes me want to say STOP! You are waaayyy overthinking this (for now), you need to stop trying to learn the tricks of the trade before you learn the trade itself. Once you get to where you can outshoot your equipment then start worrying about the minutiae. After a few rounds the temp of your barrel is not going to make you miss near as much (if any) at 1000 yards as the inconsistencies in your NPA or follow through, or even how you have your rear support set up. This is what you have a mentor for, or in your case hired an instructor. If your instructor isn’t telling you these things then my suggestion would be to find another, and I don’t care who he is/was or what kind of titles the guy has in front of his name.
If anything you should worry about the temp of your ammunition (propellant temp), try to keep it somewhat controlled.
 

ntsqd

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Going way back to the beginning, thermal conductance of pretty much every common material is well characterized. First link that popped up in a quick search: https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html
To go along with that you're going to want to know the Specific Heat of the material as well: https://www.engineersedge.com/materials/specific_heat_capacity_of_metals_13259.htm

If you are using an IR temperature gun to measure temps then the emissivity of the surface that you are measuring will affect the reading. If you are measuring different materials or different surface finishes this will introduce error in the readings. They will be consistent at each location, but each location will have an error relative to any other location. The simplest, though the least cosmetic, solution is a spot of flat black paint at all of the locations that you want to get the temperature of.
 

jfolanddvm

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Maybe I've been missing something all these years, but I have never heard anyone mention a linear (or even non-linear) relationship between barrel temperature and MV. Obviously, barrel temp can effect accuracy, but I think that has to with things other than simple velocity. Ambient temperature can obviously affect velocity in an almost linear fashion depending on the temperature stability of the powder being used, but that is way different than the temperature of the tube through which the bullet is passing. I may be wrong, but I shoot a fair bit, and much of it with a labradar, and I have never put together that my velocity gets higher with each shot in a string, although the barrel temp obviously does. Granted, once the barrel gets hot enough that I cannot comfortably hold it, I let it cool back down to near ambient temperature, so maybe if I would keep shooting after the barrel is too hot to touch, a consistent velocity change might be noticed (but I doubt it). It seems some of my barrels actually keep shooting fairly well, even when too hot to touch, but many do not, and I don't believe it is solely related to velocity. Although I've been shooting quite a while, I think it will still be a long time (probably more than I have left:) before I'm good enough that I have to worry about how much my barrel temp changes my velocity and, subsequently, my POI.
 

Jeremy Henderson

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Maybe I've been missing something all these years, but I have never heard anyone mention a linear (or even non-linear) relationship between barrel temperature and MV. Obviously, barrel temp can effect accuracy, but I think that has to with things other than simple velocity. Ambient temperature can obviously affect velocity in an almost linear fashion depending on the temperature stability of the powder being used, but that is way different than the temperature of the tube through which the bullet is passing. I may be wrong, but I shoot a fair bit, and much of it with a labradar, and I have never put together that my velocity gets higher with each shot in a string, although the barrel temp obviously does. Granted, once the barrel gets hot enough that I cannot comfortably hold it, I let it cool back down to near ambient temperature, so maybe if I would keep shooting after the barrel is too hot to touch, a consistent velocity change might be noticed (but I doubt it). It seems some of my barrels actually keep shooting fairly well, even when too hot to touch, but many do not, and I don't believe it is solely related to velocity. Although I've been shooting quite a while, I think it will still be a long time (probably more than I have left:) before I'm good enough that I have to worry about how much my barrel temp changes my velocity and, subsequently, my POI.
Very good point. I never really looked at it that way. Thank you.
 

tobnpr

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even though barrel temp definitely effects muzzle velocity
I have never seen any scientific evidence of this- please post it up?
We know that certain powders are temp sensitive, but that's a separate issue.

My concerns about barrel temps relate to not burning up the throat prematurely, and for me that means being able to grab the barrel in my hand and hold it for five seconds or so. If I can't do that, it sits a bit longer before the next string.
 

ntsqd

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I've never seen any studies on that topic either. However, metals expand with heat as do most materials. It is reasonable to propose that as the barrel heats up that both the ID and the OD grow in dimension. Not a lot at the temps we're working with, but perhaps enough to reduce the resistance of the bullet passing thru the bore just enough to show a slight velocity increase. I'd expect that statistically the increase could be confused with noise and that it would require a fairly sophisticated data gathering methodology and hardware to separate a true gain from random variation.
 

TennJed

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Barrell temp definitely affects POI based on temp and barrel thickness. Anyone that has a lever gun should be able to attest to this, due to the thin barrels, they heat up very quickly and when I first started playing with lever guns I went nuts, thinking my scope was messed up till I realized I put way to many rounds through it too quickly. At the other extreme, very heavy barrels should take longer to be affected. But as others have stated the rule of thumb should be when the barrel starts to get hot to the touch let it cool.
 

jdavistx

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Barrell temp definitely affects POI based on temp and barrel thickness. Anyone that has a lever gun should be able to attest to this, due to the thin barrels, they heat up very quickly and when I first started playing with lever guns I went nuts, thinking my scope was messed up till I realized I put way to many rounds through it too quickly. At the other extreme, very heavy barrels should take longer to be affected. But as others have stated the rule of thumb should be when the barrel starts to get hot to the touch let it cool.
An IR temp sensor is a useful tool and inexpensive. From cooking to measuring barrel temp and even testing how efficient your air conditioning is. As for powder, you should use one which has a low sensitivity to temperature variation. The data is out there.
 

ntsqd

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An IR temp sensor is inconsistent across different finishes and types of surfaces. Readings from bead-blasted and blued vs. polished and blued vs. bead-blasted SST vs. cerakote in any particular color will all be different when the metal's actual temperature is the same. Can use them to compare the same apple at different times. Can not use them to compare two different apples in any meaningful way. Forget about comparing an orange with one.
 
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