Barrel Temperature

evetseel

Well-Known Member
What’s everyone’s view on Barrel temperatures? Can excessively high temps damage a barrel? Withstanding that accuracy may be significantly impacted until cool, I’m taking long term.

I have a hunting rifle that I’m now using for load development (wasn’t the original intention). It’s got pretty hot today as I was focusing on Chrony results more than MOA. Hot as in uncomfortable to keep a hold of!
 

deeangeo

Well-Known Member
Heat = Erosion so the hotter you get the barrel the faster will be the consequences.
Depends how long you want your barrel to last.
Best not to heat the barrel excessively...allow it to cool properly, then go again.
The hotter it gets, the longer it takes to cool, especially during summer months.
 

Rider

Well-Known Member
The kind of heat that is responsible for erosion is only present on actually firing the round. But the steel will not retain these extreme temperatures for longer than seconds, it at all. This means, regardless of whether there are 10 seconds or half an hour between shots, this will not have an influence on erosion. Only the shot count as such has (all other things equal). We're not talking about a machine gun here.

The heat you can feel when touching the barrel is technically neglectable in terms of barrel wear. So I wouldn't worry.
 

ejg

Well-Known Member
Hot steel is less prone to fire cracking but possibly higher mechanical & chemical wear. Not sure about chrono results out of a hot chamber/barrel.

I did a bit of groups testing two days ago and was astonished about the barrel not getting as warm or hot as other barrels I had. The barrel was well bead blasted and sprayed in flat matt black. In theory thin matt painted black surface should improve cooling by 25% which might be the reason. I ask myself why competition shooters don't matt black spray their barrels?
edi
 

KRS

Well-Known Member
As the owner of a 25.06 I shot groups slowly when developing loads and still shoot slowly when doing any kind of range work in the hope of allowing the temperature of the barrel throat to dissipate (a bit) before subjecting it to another toasting from the next round! I fire a round, eject fired case and leave bolt open for a few seconds before loading the next, can't do any harm and hopefully extend a short barrel life a little.
 
Read this, download the spread sheet, & put in some numbers.

going from 100 second intervals to 5 second intervals, quarters the barrel life.

I run all my load data through the spread sheet. & now find it a vital tool.
Many of the traditional "favorite" powders for various calibers really are barrel burners. Sometimes a powder change might more than double the barrel life. Dropping to the next accuracy node will double barrel life again.
 

Danny Fireblade

Well-Known Member
I remember a time where we got to the last day of practice before an army shooting competition and we realised we still had a box of ammo left (800 rounds)

We bombed up every mag we had, had three people bombing up mags as 2 people put every round through 2 rifles in a quick as time as possible.

The barrels were glowing red hot, the rifles were difficult to hold as the heat from the barrels was making it uncomfortable and it sounded like we were using full auto, which we were not as not allowed on the range.

Only after did we think, hope we have not knocked zero out due to excessive use, but the following week we had a very good competition, picking up a fair bit of silverware.

I can't comment on the accuracy while we were putting the 800 rounds through it, but it never affected it afterwards.
 

Buggadifino

Well-Known Member
Temperature has a significant effect on wear but is just one of the variables in play. For those interested in the science of it the equations involved are these:




1569701661850.png

Where:

W =wear

Ao= constant (often called propellant erosivity)

d = diameter in metres

Cm = muzzle velocity in m/s

Tmax= maximum bore temperature in degrees Kelvin

X is the propellant wear coefficient at the adiabatic flame temperature and is given by:

X = (%CO) – 3.3(%CO2) +2.4(%H2)-3.6%(H2O)-0.5(%N2)


Ti = Initial Temp in Deg Kelvin
Tf = Flame temp in deg kelvin
d = diameter in metres
m = mass of propellant in kilo
Cm = muzzle velocity in m/s

As I say temperature can be significant: a reduction of 20% from1000 dec C (which can be achieved in machine guns or other large quick firing guns - as soon as I can get the graph of the current format I will share it) will reduce wear by twenty times. Not, perhaps, an issue for bolt action rifle owners but if barrel longevity is your aim then running it hot consistently will shorten your barrel life.

PS apologies for the format of the equations - equation editor does not work here.

Best regards,

Andy
 

deeangeo

Well-Known Member
While I’m definitely not a person with great technical knowledge in this respect, it isn’t just heat by itself causes barrel wear. Friction and heat combined is what does the damage.
It must therefore follow that to optimise barrel life, it has to be better not to run long strings of shots, particularly in the lighter weight sporting barrels.
 

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