Over heated barrel?

K

kschatzle

Inactive
Greetings,

I am new to shooting and got a little carried away the other day and shot about 60 rounds in less than 1 hour through my Browning White Gold Medallion Stainless Steel 7Mag with Boss.

I kept wondering why the scope was seeing waves - heat, I later figured out.

The barrel was far too hot for me too touch, so I mentioned it to the range owner and he informed me it is bad to let it get so hot.

The rifle is beautiful and highly accurate - so I am wondering if I have screwed it up permenantly. I would also appreciate some general commentary on this matter - thanks

Kevin
 
The range owner was correct, it is not good to get it that hot. However you will have to shoot it again to see if it affected the accuracy at all. If you let it cool slowly it might be ok. I once got my sks barrel so hot it gave me a 2nd degree burn from brushing it on my arm. That did not seem to affect that gun but it was not that accurate to begin with. If it still shoots the same all is well.
 
More than likely it'll be OK. When the barrels are that hot, they tend to wear out quicker, at least that's what I was always taught. Maybe someone with more experience will chime in and correct me.

Typically with my .30-06 I wait at least 2 minutes between shots, and give it a good 5 minutes or so between groups. In the dead of summer I give it even more time. With my .223 bolt, I don't really keep up with times, just remembering to give time for my eye to rest, etc.

Definitely if it's too hot to touch, its too hot. Not to mention when it gets hot it won't shoot as accurately. Your groups will start to open up.
 
Here's the scoop. A rifle barrel is quenched to an "as-quenched" hardness of HRC 52 which is too hard (brittle) for the application. Any steel which is quenched must be "tempered" afterwards to relieve stresses. I've seen large steel gears blow into two pieces right next to me because they didn't get in the temper furnaces soon enough. It sounded like a .300 Win Mag going off! (I'm a retired metallurgist).

So the heat treater must "temper" this barrel he just quenched (HRC 52 approximately) down to the desired hardness for this application which is HRC 32-36 (usually). If he did not want to change the HRC 52 "as-quenched" hardness he would temper at approximately 300º-375º F. To get it to drop to the 32-36 HRC range you have to temper (usually 4140 steel or 400 series stainless steel) at around 1000º-1100º F.

Now you can see how hot you have to get it to hurt it (over 1000º F). And the barrel won't change color until around 1500º F so you haven't hurt your gun. You can't touch a barrel if it's 150º F.

One more note... Stress relieving is done after heavy machining and is usually done at 1000º F (after quench and tempering and then machining). By getting the barrel hot you "might" relieve some machining stresses and have the point of impact change (permanently) but the barrel is not damaged.

Tempering and stress relieving are basically the same heat treat process in the same kind of furnace but have different names because they are done for different reasons.
 
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Hello, While I agree with warbirdlover on the fact that the barrel would have to reach critical heat treat temp. to be damaged. However, in this case, we are not talking about the WHOLE barrel...only the inside surface of the bore..perhaps less than .00001"..If this "skin" becomes overheated, it can become hardened to the point where it will begin to craze or crack...extreemly slight at first, but will worsen over time, as more heat & pressure is applied to it. Being Stainless, it is more resistant to this wear than Chrome-Moly.
 
Is the bore in my Norinco SKS chrome-moly?

I used 30 rounds of Wolf/Monarch in about 15 minutes yesterday, and it was about 75* outside.
The shooting had to stop due to the ambient temp, but the ammo was gone anyway.

This is not allowed on hot summer days because the barrel gets too hot after 10 rds. in about 5 minutes.
 
Is the bore in my Norinco SKS chrome-moly?

I used 30 rounds of Wolf/Monarch in about 15 minutes yesterday, and it was about 75* outside.
The shooting had to stop due to the ambient temp, but the ammo was gone anyway.

This is not allowed on hot summer days because the barrel gets too hot after 10 rds. in about 5 minutes.
Today 12:36 AM
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The SKS is a combat arm, there is no way 30 rounds in 15 mins should come anywhere near the heat limit for that weapon. In Fact i would hazard to guess 300 rounds in 15 mins are not beyond the scope of the weapons' intended rate of fire.
 
60 rounds in an hour probably did not hurt the barrel. But don't try to get the barrels hot, especially with over bore magnum cartridges. Those rounds really eat barrel throats.
 
You likely didn't harm it, but I wouldn't make a habit of shooting it like that again.

I usually shoot mine in 5 round groups and then let it cool a bit before I pick it up again.
 
Heat per se wont hurt the barrel, it can effect accuracy while hot.

Having said that, the fire from the burning powder will eat the throat over time. I have a 300 Winchester Target rifle and have gotten it "hot" several times. I think its round count more then heat. When I made this rifle I started with a 29 inch barrel, bedded is so as accuracy isn't affected by heat. When I see accuracy start to go (and it will go faster with the magnums I set the barrel back. Meaning I take it out of the action, cut off 1/8-1/14 inch (depending on how bad it is) re-chamber it, and its like a new barrel.

I don't believe 60 rounds is enough to hurt a 7 RM.

What ruins barrels more then anything else, including getting hot, is improper cleaning. Clean from the chamber end if possible, never use jointed or coated cleaning rods. The one piece stainless steel rods are the best. Only put the jig one way, meaning push it out the end of the barrel and take it off before you bring the rod back out. (different subject).
 
Ideal Tool,

To "harden" it would have to reach a temperature of 1500º F or more. The color of the barrel would be orange and if you loaded a cartridge in a bore that hot I guarantee you it would fire all on it's own, in a very short time.

The "skin" inside would not heat significantly hotter then the whole barrel either as the heat is steadily carried throughout the rather thin barrel cross section. And to "harden" it needs to be "quenched". There is no "quenchant" inside the barrel (oil, water, cold air).

If you still don't believe me there is a way to tell if any heat damage occurred. Check the hardness in the chamber with a a "test file" hardened to HRC 32. If the file doesn't "bite in" the heat did not temper back (soften) the chamber. But I wouldn't do it if you don't know how to use them as you could damage your barrel throat for maybe no reason at all.

http://www.muggyweld.com/color.html
 
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Have you screwed it up permanently?
No.

Did 60 shots in "less than an hour" cause more erosion to the throat than 60 shots fired five or ten at a time with thorough cooldown between strings?
Yes.

So you put maybe 100-200 rounds worth of wear on the gun with 60 shots through a barrel too hot to touch. It's your gun.


Kraig,

I never heard of 1/8 - 1/4 inch of setback. Most of the shooters I know of set their barrels back at least an inch, maybe two, to be sure of a clean throat.
They usually do it only once, though.
 
I seriously doubt you hurt the barrel at all. 60 rounds in an hour is nothing. Any gun should be able to fire that without any problem whatsoever.
 
Kraig,

I never heard of 1/8 - 1/4 inch of setback. Most of the shooters I know of set their barrels back at least an inch, maybe two, to be sure of a clean throat.
They usually do it only once, though.
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Take a look at a throat erosion gage, it doen't that that much. We're not talking about a total destroyed barrel, we are talking them (targer rifles) getting to the point where your accuracy starts to go south.

And you can do it more then once. I've done it 4 times on this barrel, and it shoots quite well. This is a Single shot Model 70 in 300 WM, I use 200 Grn SMKs.

1000%20yd%20Rifle.jpg
 
I've had a stainless AR-15 barrel so hot it turned straw color. The POI driftet while it was that hot, but accuracy and POI came back when it cooled down.

Shooting a hot barrel will cause incrementally more wear than shooting it cold, that's about it.
 
Shooting a hot barrel should not cause any more wear then shooting a cold barrel because the hardness is the same. The hardness determines how much wear will take place and that hardness at different temperatures is the same until you get it over 1100º F. And I don't think that's possible unless you're shooting a machine gun.
 
Shooting a hot barrel should not cause any more wear then shooting a cold barrel because the hardness is the same. The hardness determines how much wear will take place and that hardness at different temperatures is the same until you get it over 1100º F. And I don't think that's possible unless you're shooting a machine gun.
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When barrels "wear out", it's usually because the throat has eroded to a point where the accuracy has degraded past a certain criteria (1 MOA or whatever the shooter needs). The flame temperature of smokeless powder is in the range of 3300 degrees F. The throat takes the brunt of this temperature/pressure. I don't have data to back this up, but it would be reasonable to think that the surface of the throat section (or more of it) can get hotter if it starts at 600F than if it starts at 90F.

-z
 
What you are saying is correct but it has nothing to do with barrel (steel) temperature. It is the flame temperature which WILL erode the barrel. Two different things. It's due to more shots being fired and not how hot the barrel gets. A .300 Win Mag will erode a barrel much faster then a .30-06 due to the higher flame temperature. Do we agree now?

:confused:
 
i didnt even think it mattered. i shot 1 round a second until the barrel was smoking and i still kept firing. yes the barrel was ultra hot. the handguard was even hot.
 
What you are saying is correct but it has nothing to do with barrel (steel) temperature. It is the flame temperature which WILL erode the barrel. Two different things. It's due to more shots being fired and not how hot the barrel gets. A .300 Win Mag will erode a barrel much faster then a .30-06 due to the higher flame temperature. Do we agree now?
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So you're saying that 3300 F flame temperature won't ever heat the surface of the throat more than 1100 F. I don't believe that. If that were true then you could never the the bulk of the barrel over 1100F due to how heat transfer works (ie, delta t), and I've measured MG barrels over that temp myself.

When you weld something, or cut it with a torch, the surface gets super hot - enough to melt the metal - but just a few mm below the surface it's still solid; thus there is a gradient of temperature. This logic applied to the throat would suggest the surface of the throat gets hotter than the retained temperature of the barrel in the throat area, given a gas temperature of over 3000 F.

With regard to .300WM vs. .30-06, if the pressure is the same and the powder technology is the same, the flame temperature should be close to the same. The .300WM would have more throat erosion due to dwell time.
 
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