Heat vs thickness of barrel

[NC/Br Shooter]

This is not an exact science that I am aware of.
The different barrel contours that are out there have their purpose. The one you choose is for the purpose or discipline you pursue. Weather it's to make weight or you just want a particular one.
Some feel a certain kind gives better accuracy.

In the topic of holding off heat. Would you say a 1.25 straight contour would heat up slower than a 1.00 inch straight contour?
And if so, would this not let the shooter get more shots down range before the groups start to open up.?

My answer to this differers from a friend of mine. And I just wanted to post this question here to get some feedback.
Thanks

 

[Cfshooter]

I think the thicker the longer it takes to heat up, and cool back down.

 

[JLT]

In this context, one can think of the barrel as nothing more than a heat sink. Two things matter (actually three, but we're limited to steel in this case) respecting the efficiency of a heat sink - mass and surface area. The greater the mass and the greater the surface area, the more efficient the heat sink. A 1.25" straight has quite a bit more mass than a 1.00" straight and materially more surface area, therefore it is a more efficient heat sink. All other things being equal, the larger tube is better able to dissipate heat than the smaller tube.

 

[jelenko]

get more shots down range before the groups start to open up

Once a barrel warms/heats up, the size of the groups settle down.
Also, if there's little to no residual stress in the barrel, the POI will not move.

 

[SteveOak]

Fluting will increase surface area. The barrel should heat up slower, will cool down faster and will be stiffer.

 

[C.E.Smith043]

Fluting will increase surface area.
The barrel should heat up slower, will cool down faster and will be stiffer.

Fluting will increase surface area. TRUE
The barrel should heat up slower. FALSE
will cool down faster. TRUE
and will be stiffer. FALSE

 

[NC/Br Shooter]

Basically, The groups are smaller shots 0- 30 than they are 30-60.
warm as opposed to really hot

 

[Keith Glasscock]

Dimensionally, the barrel changes with temperature. I suspect this has a lot to do with your observation.

 

[dusterdave173]

Shilen says do not flute--it is in FAQ
When it is hot enough for groups to open it is past time to swap out rifles in the PD field

 

[SteveOak]

Fluting will increase surface area. TRUE
The barrel should heat up slower. FALSE
will cool down faster. TRUE
and will be stiffer. FALSE

If fluting increases the rate of cooling it MUST also decrease the rate of heating.

Rate = temperature delta/time

 

[JLT]

If fluting increases the rate of cooling it MUST also decrease the rate of heating.

Rate = temperature delta/time

The amount of energy (heat) is independent in this case, determined by an outside agent (the chemical reaction of firing a round in the chamber). The resultant energy is a constant. What will vary is how the mass will dissipate that energy. Said differently, a round will not be 'cooler' in a fluted barrel. The greater surface area of a fluted barrel will dissipate heat (energy) more quickly, and this may appear to the observer that it 'heats up' at a different rate.

ETA - And no, a fluted barrel is not stiffer. It is not possible to increase structural integrity by removing material.

 

[fkimble@charter.net]

Nothing magical here, pure physics.

Frank

 

[jelenko]

My understanding is that a fluted barrel is stiffer than a barrel with the same mass and length but non fluted.

 

[SteveOak]

The amount of energy (heat) is independent in this case, determined by an outside agent (the chemical reaction of firing a round in the chamber). The resultant energy is a constant. What will vary is how the mass will dissipate that energy. Said differently, a round will not be 'cooler' in a fluted barrel. The greater surface area of a fluted barrel will dissipate heat (energy) more quickly, and this may appear to the observer that it 'heats up' at a different rate.

ETA - And no, a fluted barrel is not stiffer. It is not possible to increase structural integrity by removing material.

You are conflating the amount of heat induced into the barrel with the actual question which is the resulting temperature of the barrel.

You should probably study up on how increasing the surface area affects stiffness. An I beam will be stiffer than a rod of the same length, material and mass.

Also, I did not see structural integrity mentioned previously.

 

[Uncle Bruce]

You are conflating the amount of heat induced into the barrel with the actual question which is the resulting temperature of the barrel.

You should probably study up on how increasing the surface area affects stiffness. An I beam will be stiffer than a rod of the same length, material and mass.

Also, I did not see structural integrity mentioned previously.

If you could measure the temperature of the bore v. Temperature of the outside of the barrel, would the speed of the temp change be the same for different barrel sizes? What I am looking at would be speed of throat erosion.

 

[urbanrifleman]

The difference in mass will account for a difference in how long it heats up. No doubt about that.

My guess is that the difference would be so small as to be a non effect, and would not account for the performance difference you are observing. It's most likely something else.

 

[JEFFPPC]

Fluting will increase surface area. The barrel should heat up slower, will cool down faster and will be stiffer.

According to what the AMTU put out a few years ago on this forum, that is a false statement.

 

[FrankG]

Fluting will increase surface area. The barrel should heat up slower, will cool down faster and will be stiffer.

I'll say no, maybe and how are you measuring the stiffness? On the last part of being stiffer I can say no and I can say yes.

In the grand scheme of things.... it's cosmetic.

Later, Frank
Bartlein Barrels

 

[jxb]

If you could measure the temperature of the bore v. Temperature of the outside of the barrel, would the speed of the temp change be the same for different barrel sizes? What I am looking at would be speed of throat erosion.

You might ask the Hornady folks to test that in the lab. It would be easy enough for them to do that with a couple wore out barrels of different dimensions and they could replace the pressure sensor with a temp sensor to get your internal temp for comparison. Meaning they have the means to provide actual data on this subject and if they haven't already done that test likely would be curious enough to do it.

That said, steel is not a good conductor of heat so it would stand to reason that rapid fire of xx rate would overwhelm the ability of the steel to pull heat away from the bore fast enough to keep the bore temp stable, regardless of diameter. I'm thinking it wouldn't have to be very rapid rate of fire to do this based on my experiences with 220 Swift before I learned to slow down and swap out rifles while shooting sage rats.

This is evident when you leave a round in the chamber for a set amount of time, say xx seconds, and compare the temp of that round or spent brass when you eject it (fast rate of fire vs slow). I've had the barrel where I could leave my hand on it, but I almost couldn't hold the ejected brass or round. Usually this was a round I'd eject for whatever reason and I immediately realize I was firing too fast and needed to slow down. I have learned since those days, but that barrel's first 4-7" looks like canyon land. Amazingly when I pulled it from service it was still shooting about 1.25moa (old M77V)

 

[FrankG]

Inside of the bore of the barrel will always heat up faster than the outside of the barrel. If I recall correctly the heat temp at the throat area every time you shoot around the flame temp is around 2200-4000F depending on the powder/cartridge etc...your not stopping what's happening inside the bore every time you light that round off.

On a temperature test we just ran exactly a year ago... it was a short test but from a cold barrel (308win was the caliber on both of them and we shot an all steel barrel and a CFW barrel at the same time and same cadence) the inside of the barrels (we measured the chamber end and muzzle end on both inside and outside of the barrels) for every 3 rounds fired the temp jumped basically 10 degrees for every 3 rounds fired. This basically applied to each one. The all steel barrel (M40/M24 contour) didn't heat up as fast as the CFW barrel by only a few degrees but once up to basically the same temp... the CFW barrel on a measured 7 min cool down period did cool to a cooler temperature than the heavy all steel barrel did.

Again though... you are not stopping what's happening to the inside of the bore of the barrel during shooting.

Later, Frank