[HisDivineShadow]

I have an 870, I recently removed the rifle sight on it by using a propane torch, the sights themselves where glowing red hot before the soldering let go, the barrel was glowing around the area too a bit. I have not actually shot the gun since but I am not fearful I might have ruined the tempering at the muzzle and near the rear sight. Is there any simple way to check this? Can a gunsmith re-temper the barrel or is that beyond what they usually have access to? Need a dedicated metalworker perhaps?

I'm thinking of simply loading it up with various ammo and shooting using a string or something :p

Shoulda just bought a new barrel... but I can't find any 20" barrels without rifle sights, I just want a bead...

[LongRifles, Inc.]

If it took that much heat to remove the sight it more than likely means it took that much to install it.

I'd shoot it like I stole it.:D

[Clipper]

...In a word, no.

[HisDivineShadow]

I did dip it in water to cool it afterwards, I read that is a big no-no, makes the steel hard but brittle. I forgot to mention that in my first post, it wasn't red hot when I did that since it had time to cool, only took a few seconds.

[rcmodel]

Well, you shouldn't have done that.

All bets are off if you tempered it in cold water.

I wouldn't say it isn't safe now, but I wouldn't say it is either.

rc

[W.E.G.]

I doubt you did any harm if the barrel was not still glowing.

We shot an AK-47 all day, and when it needed cooling we dunked the whole front end of the gun in a bucket of water so we could keep shooting.

...and it DID keep shooting.

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/AK-47/DSCN2187.jpg

[Clipper]

Shotgun powders are fast burning, and the pressure surge is all over after 10-15" or so. By the time the charge is out to the muzzle, the barrel could be made of JB Weld and would likely be OK, especially with a cylinder bore.

[rcmodel]

From the OP's question:
tempering at the muzzle and near the rear sight. I'd guess the rear sight was nowhere near the muzzle.

Most likely way closer to the chamber, and the high pressure.

rc

[docsleepy]

tempering is done at various temperatures if I remember, and I think they are lower than redhot.

I think I would read up on the internet to find out what hardness of steel is used for that type of barrel, and how to temper roughly to that hardness, then reheat JUST the rear area you're concerned about and allow it to cool in the manner needed to temper properly.

Or change the barrel

[docsleepy]

OK, I found an article that gives the hardness of shotgun barrels:

http://www.accessmylibrary.com/coms2/summary_0286-32471845_ITM

"In fact, shotgun barrels are made of relatively soft steel, within the range of 115 to 117 on the Diamond Pyramid Hardness/Vickers (DPH) scale, or 65.0 to 70.0 on the Rockwell-B scale. Not only are shotgun barrels made of relatively soft steel, they're also very thin."

[docsleepy]

And I found that hardening and tempering are different shades of the same thing:

People usually harden (which you did, by dropping it in the water) and then temper, to adjust the hardness:

http://www.1911encyclopedia.org/Hardening_And_Tempering_Annealing



The distinction between hardening and tempering is one of degree only, and both are of an opposite character to annealing. Hardening, in the shop sense, signifies the making of a piece of steel about as hard as it can be made - "glass hard" - while tempering indicates some stage in an infinite range between the fully hardened and the annealed or softened condition. As a matter of convenience only, hardening is usually a stage in the work of tempering. It is easier to harden first, and "let down" to the temper required, than to secure the exact heat for tempering by raising the material to it. This is partly due to the long established practice of estimating temperature by colour tints; but this is being rapidly invaded by new methods in which the temper heat is obtained in furnaces provided with pyrometers, by means of which exact heat regulation is readily secured, and in which the heating up is done gradually. Such furnaces are used for hardening balls for bearings, cams, small toothed wheels and similar work, as well as for tempering springs, milling cutters and other kinds of cutting tools. But for the cutting tools having single edges, as used in engineers' shops, the colour test is still generally retained.

In the practice of hardening and tempering tools by colour, experience is the only safe guide. Colour tints vary with degrees of light; steels of different brands require different treatment in regard to temperature and quenching; and steels even of identical chemical composition do not always behave alike when tempered. Every fresh brand of steel has, therefore, to be treated at first in a tentative and experimental fashion in order to secure the best possible results. The larger `he masses of steel, and the greater the disparity in dimensions of adjacent parts, the greater is the risk of cracking and distortion. Ex increase the have to be g. A grade of steel must be selected of suitable quality for the purpose for which it has to be used. There are a nhzmber of such grades, ranging from about z z to z % content cif carbon, and each having its special utility. Overheating must be avoided, as that burns the steel and injures or ruins it. A safe rule is never to heat any grade of steel to a temperature higher than that at which experience proves it will take the temper required. Heating must be regular and thorough throughout, and must therefore be slowly done when dealing with thick masses. Contact with sulphurous fuel must be avoided. Baths of molten alloys of lead and tin are used when very exact temperatures are required, and when articles have thick and thin parts adjacent. But the gas furnaces have the same advantages in a more handy form. Quenching is done in water, oil, or in various hardening mixtures, and sometimes in solids. Rain water is the principal hardening agent, but various saline compounds are often added to intensify its action. Water that has been long in use is preferred to fresh. Water is generally, used cold, but in many cases it is warmed to about 80° F., as for milling cutters and taps, warmed water being less liable to crack the cutters than cold. Oil is preferred to water for small springs, for guns and for many cutters. Mercury hardens most intensely, because it does not evaporate, and so does lead or wax for the same reason; water evaporates, and in the spheroidal state, as steam, leaves contact with the steel. This is the reason why long and large objects are moved vertically about in the water during quenching, to bring them into contact with fresh cold water.

[docsleepy]

And I found the beginnings of telling you to temper the area you have over-hardened...but I haven't yet found quantitative info on exactly to how reach the right hardness...

http://www.1911encyclopedia.org/Hardening_And_Tempering_Annealing


Temperature.
Color.
Temper.

430o
Very faint yellow.
Very hard; suitable for hammer faces, drills for stone, etc.

450o
Pale straw color.

470°
Full yellow.
Hard and inelastic; suitable for shears, scissors, turning tools for hard metal, etc.

490o
Brown.

510o
Brown with purple spots.
Suitable for tools for cutting wood and soft metals, such as plane irons, knives, etc.

538°
Purple.

550°
Dark blue.
For tools requiring strong cutting edges without extreme hardness; as cold chisels, axes,cutlery, etc.

560o
Full blue.

600°
Grayish blue verg- ing on black.
Spring temper; saws, swords.


However, probably some blacksmith could give you much better information!

[HisDivineShadow]

Well this was pretty smoking hot, I think the sights where brazed, not just silver soldered on given how much damn heat I had to apply to take 'em off. I have a friend with metalworking skills, he says you need to keep the barrel in a tempering oven at a specific degree etc. All very complicated and requiring the right amount of tools.

I have 30 or so trap shells and 20 winchester slugs to put through this gun later today, I'll make some kind of setup so I can fire it remotely, lets see what happens...

[Miked7762]

If you aren't absolutely married to the 20" length, Mossberg makes a 18.5" barrel with a bead sight for the 870.

[HisDivineShadow]

I have a +3 extension that fits the 20" but not the 18.5" so it would be preferrable. Also I am located in Finland I have not seen any spare barrels for sale anywhere, the closest I got was a 23" of the wrong config anyway and it was 275 euros (330$ maybe)...

[gun nut]

To be honest shotgun barrels traditionally received little or no heat treatment. Many barrels are silver soldered together nowadays (it stops the problem of your barrels separating when caustic bluing them:what:) and are cooled naturally removing most of the hardness in them. Quenching the barrel could however of hardened it - remember natural cooling in the air can act as a quench! Gentle heating with a gas torch would be fine for drawing any temper to ensure the barrel was not too brittle!

[HisDivineShadow]

I test fired it today, ran 6 slugs through it and 10 trap shells, no problems. I did encounter a weird thing though, the lower quarter of the barrel, just near the muzzle has a tiny bulge, I can feel it runing my fingers over it, and barely see it when I hold it to the light. This is weird, I am not sure if it was there before or not. Also I would expect cracks, not bulges (indicative of being too soft, not brittle).

The area near the rear sight looked entierly unaffected though.

[RoostRider]

You must be a gambler....

I wouldn't have heated a barrel like that.... but if I had I sure wouldn't shoot it.... but if I did, and it didn't rupture, I sure wouldn't consider that proof that it was still safe.... (especially if I noticed an anomaly....)

But meh..... you've already gone way further with it than I would have....

[72IH]

The color temp guide is a little more tricky than just looking at the color. It all relies on oxidation. If you put the flame directly on the bare steel it will react much faster than if you heat it a distance away. It would only be the surface that reaches the temp with a direct heat source. It also relies on how clean the surface is, oils will throw it off by changeing how much oxygen is allowed to contact the surface. You want it to be clean and polished to be accurate.

Now I would trust this method to make chisels and knives any day, but never an object that has an explosing going on inside of it.

[HisDivineShadow]

You must be a gambler....

I wouldn't have heated a barrel like that.... but if I had I sure wouldn't shoot it.... but if I did, and it didn't rupture, I sure wouldn't consider that proof that it was still safe.... (especially if I noticed an anomaly....)

But meh..... you've already gone way further with it than I would have....
Well, I read up on the internet and got the impression that plenty of people removed the rifle sights on their 870 barrels by heating them up so it did not appear to be dangerous or even that uncommon.

The information I got indicated that the tempering would not be affected until at far higher temperatures than I would go with my torch, it was by coincidence that I got conflicting reports on that idea when I was looking intro the nitre bluing process.

As for shooting it, I rigged up a stand and pulled it using a 6 foot long string and using safety glasses :p

I'm still not convinced of it's safety though, I would like to do some rockwell testing on the areas that where affected by the torch and the ones that where not.

[evert]

easiest way to see if the barrel is "hardened" is to use a file... since you probably have to refinish the thing anyway.

[RoostRider]

Sounds like you got it going the right way.... except for the 'read up on the internet' thing.... as you've noticed, 'conflicting reports' are almost inevitable with a resource that is 'anyone who feels like commenting on a global scale'... I wouldn't trust a word of it with my safety... confirm through solid sources

I wasn't trying to harsh out on you.... There was a day when I would have taken similar advice from someplace like the internet.... these days I just look at old wounds and go, "nah, not worth it"... :)

I am glad to hear you are taking a lot of safety precautions (that's what kept me alive during those days... lol)....

[HisDivineShadow]

I did take a file and sandpaper to it to fix some cosmetic imperfections, the file had no problems cutting the metal, certainly far easier than it was fixing up my norinco 1911 (http://forum.m1911.org/showthread.php?t=73061)(known for their notoriously hard steel).

[gun nut]

As I said most shotguns have no heat treatment on their barrels. Many doubles are silver soldered or even brazed together and receive no heat treatment afterwards. However a bulge could be serious and I would consider getting a gunsmith to give it a once over to assess how bad it is.