Thread: What's the Deal?

Originally Posted by Norway

Shooting Chrony is not bad, it's just that they are light dependant and reading will vary with the light.

I know no problems with mine when used in clear direct sunlight, readings appear 'accurate' and have done so for the 5 years I've had it. Even put it next to jake wires (he didn't trust his) and they read the same.

The super chrono looks nice for more portability though.

Originally Posted by Norway

No you lose approximately 30 msec doing that.
To stay within sane pressures, I think it would be difficult to bring a 260 up to 830 msec in a 20".

Sorry normie for the steel an cut an paste of your info..........
As the title suggests I did a ladder test recently with my 22" .260 and below are the results.

Load details:
OAL 2.865" (mag length)
140gr A-Max
.260 Lapua Brass
CCI BR Primer
Hodgdon Hybrid 100V Powder

41gr - 2556
41.5gr - 2583
42gr - 2632
42.5gr - 2704
43gr - 2693 (1st shot after letting barrel cool for a little while)
43.5gr - 2744
44gr - 2797
44.5 - 2879 (Definitely load too hot. Major extractor mark and tight bolt lift)

Going by the little loss is speed you are saying norway that shows me the smaller case of the 260 beating an lasting longer than your 6.5-284 witch i think personally is a pig or a cal apart from in a longer target barrel shorter barrel may as well go smaller better counterpart

What about parallax? Could it cause a .8 mil shift in POI? I might not have adjusted the parallax before shooting. Can't remember.

maybe.

Fuck Tussock, I didn't realise what a genius you were.

I didn't understand anything you said in that post, went right over my head with that one.

Does that make fluting a heavy barrel a waste of time as it would be letting the heat escape in certain places making those waves of heat not equal?

Lighter weight without compromising stiffness is the other reason.

Would having barrels that are tapered have an effect on accuracy? the heat taking longer to escape on the fatter end and so on?

Originally Posted by Tussock

No, the waves of heat was a figure of speech really. More surface area to dissipate heat is probably the only practical reason for fluting.

And weight

Sent from my GT-I9300T using Tapatalk 2

Yeah I'm not really into fluting

Thanks Tussock I have been thinking about trying to express sensibly the thick/heavy/hot internally barrel theory for a while.

Some of the Target guys fire a heap of rounds in fairly short time.

I have often wondered how the Carbon wrapped barrels get on with thier very thin metal barrels surrounded by resin etc.

The heat has to get out & away from the throat as fast as possible to avoid excessive erosion.

I noticed a while ago now that you could fire 10 shot mag or two out of my 338 Norma 98B Barrett & it would stay reasonably cool.

The alloy chassis would heat up taking the heat quickly out of the barrel, it has a big shank/shoulder area around & in front of the chamber which has plenty of contact with the chassis.

Fluting is mainly cosmetic I believe, with a small decrease in weight & increase in surface area.

A fluted barrel will be stiffer than a barrel of the same length & weight.

I am not sure I am following your reasoning Tussuck.
A thinner / lighter barrel will erode slower because although it heats up faster it also cools down faster… therefore the bore surface temperature would be lower when firing the next shot... I think this would only be the case after a certain amount of shots and a certain time frame.

I absolutely agree with you that both a heavy and a light barrel will see the same heat input. But I would have thought that heat transfers much faster through steel than it does from steel to air. My line of thinking is that the heat would average over the mass of the barrel faster than it would be dissipated from the outside surface to the air. This would mean that the heavier barrel will absorb that heat and remain cooler after a short time when compared to a lighter barrel.

This is how I interpret Greg’s observation above as well. His rifle chassis is sucking the heat out of the barrel faster than the heat would normally dissipate from the barrel outside surface.

I would agree with you Gillie. My understanding is that a thicker heavy barrel is essentially a giant heat sink. And as such requires more energy to heat in its entirety.

Think of trying to use a gas torch to weld together thick steel, requires a lot more time to heat than a thinner piece as the heat is conducted and diffused throughout the entire piece.

Just some light thermal dynamics reading taken from wiki

Heat conduction, also called diffusion, is the direct microscopic exchange of kinetic energy of particles through the boundary between two systems. When an object is at a different temperature from another body or its surroundings, heat flows so that the body and the surroundings reach the same temperature, at which point they are in thermal equilibrium. Such spontaneous heat transfer always occurs from a region of high temperature to another region of lower temperature, as described by the second law of thermodynamics.

Conduction
Main article: Thermal conduction
On a microscopic scale, heat conduction occurs as hot, rapidly moving or vibrating atoms and molecules interact with neighboring atoms and molecules, transferring some of their energy (heat) to these neighboring particles. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another. Conduction is the most significant means of heat transfer within a solid or between solid objects in thermal contact. Fluids—especially gases—are less conductive. Thermal contact conductance is the study of heat conduction between solid bodies in contact.[6]
Steady state conduction (see Fourier's law) is a form of conduction that happens when the temperature difference driving the conduction is constant, so that after an equilibration time, the spatial distribution of temperatures in the conducting object does not change any further.[7] In steady state conduction, the amount of heat entering a section is equal to amount of heat coming out.[6]
Transient conduction (see Heat equation) occurs when the temperature within an object changes as a function of time. Analysis of transient systems is more complex and often calls for the application of approximation theories or numerical analysis by computer.

A heavier barrel also offers a larger surface are, probably around 2x, with which it can dissipate the heat. So a heavy barrel should dissipate a certain amount of energy quicker than a standard profile.