26 Nosler - Crazy Barrel Temp

[Engineering101]

I've been working up some loads for my 26 Nosler. While waiting for the barrel to cool I noticed something I haven't seen before. Out past the end of the scope the barrel was hot while the first 5 inches or so including the chamber area was cool. It was like it hadn't been fired. One I noticed this I kept checking thinking the heat would eventually soak through the thicker chamber area but it never did. The obvious conclusion is that the powder isn't burning near the chamber but is burning down the barrel past the end of the scope. It did the same thing on the next shot and the next and the next. I hadn't noticed this previously because I was using other rifles while the 26 cooled so I just fired it and put it on the rack.

This is pretty crazy in my book because the powder should be having a hard time getting out of the case and thus more of it should be burning in the case. However, I know basically nothing about barrels and powder combustion so I'm hoping that one of you more knowledgeable guys can clue me in? Thanks in advance.

The load was 77.5 grains of Magnum which is a half grain under the minimum load per Nosler data. Velocities ranged from 3,330 to 3,400 fps with the 127 LRXs out of a stainless 26" 5R Krieger with a 8.5 twist. (Seems like the barrel is kind of tight so velocities are up compared to the Nosler data.)

 

[Edd]

You should be pleased. If the powder isn't burning near the chamber, you won't have any throat erosion.

 

[Buttermilk]

My 300 RUM and 30-338WM exhibit the same trait. Both of these barrels get hotter just ahead of the scope compared to just at the chamber/throat area.

 

[upacreek]

Soomeone can argue my position, but it seems the powder isnt going to heat the barrel nearly as quickly as the shear friction of the projectile dragging itself down the barrel. I would also be more concerned about unburned powder erroding the throad due to sand blasting effect more than heat transfer. I know we always hear its the heat that kills barrels, but larger coarse propellants like 4831 would be much more abrasive at that velocity than just making the barrel hot for a micro second. This is just my uneducated beleif, so take it for what it is.

 

[AZShooter]

IMO it isn't your chambering but the slower powder. I have noticed this for years. The slower burning powder will have a peak temperature somewhere down the barrel. I used an infra red gun a number of years back to check for ambient and also as to how hot a barrel got. Heck if you feel every barrel after 2-5 shots you will begin to notice that some powders will make the barrel its hottest mid length or even past midlength of the barrel.

 

[davkrat]

All of my guns so that. I assumed it has to do simply with the thickness of the steel. I can't imagine that powder simply is not burning in the first 5" of a barrel. That seems ridiculous. Now I know powder continues to burn down the length of the barrel but that doesn't mean it is not burning and burning hot at the mouth of the cartridge.

 

[Varminator 911]

I think that effect is mainly how thick the steel is not where the powder burns. The thicker the steel the slower it warms up.

The other factor at play is temperature is proportional to pressure. If you take room temperature air and compress it to 60,000 psi. it will get extremely hot even with no heat added from burning powder. So even if no powder burned inside the cartridge case it would still be very hot there because of the pressure. Inside the case is also held at high temperature longer than further down the barrel because high pressure lasts longer inside the case than anywhere else. Near the muzzle pressure is lower and pressure pulse shorter.

Even in a 26 Nosler powder is burning inside the case. Not all by any means but some.

 

[Engineering101]

This is a pretty confusing one because I burn the same powder in my 338 RUM (which is the same case as the 26 Nosler) and it gets hot down the whole length of the barrel (especially around the chamber). There is something different about the 26 (obviously a much smaller hole in the case) that is causing this. This is not about the thicker metal because the thicker metal in all my other rifles gets as hot or hotter than the middle of the barrel. I'm also going to try the 26 Nosler with some US 869 and H50BMG (the other two powders Nosler lists load data for) for a fuller case and hopefully improved accuracy and I'll see if they heat the barrel the same way.