Dunking a hot AR barrel in water?

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Theoretically, dunking the hot barrel in water would harden it (Google quenching).

I'm not sure if it would change the straightness of the barrel though.
 
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Theoretically, dunking the hot barrel in water would harden it (Google quenching).

I'm not sure if it would change the straightness of the barrel though.

Couldn't it also make it more easily "shattered"? I believe barrel steel is designed to be strong but still have some flex to it, if you increase the "hardness" it would become more likely to shatter I would think.

I'm no materials engineer but I did stay at a Holiday Inn Express!
 
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Couldn't it also make it more easily "shattered"? I believe barrel steel is designed to be strong but still have some flex to it, if you increase the "hardness" it would become more likely to shatter I would think.

Not sure, really.

I wouldn't do it, but the OP's mileage may vary.
 

flintoid

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Couldn't it also make it more easily "shattered"? I believe barrel steel is designed to be strong but still have some flex to it, if you increase the "hardness" it would become more likely to shatter I would think.

I'm no materials engineer but I did stay at a Holiday Inn Express!

you are correct. Aggressive hardening steel also makes it more brittle. But it'd have to get pretty damn hot in order to increase it's hardness properties. "Shooting hot" wouldn't do anything I don't think.

And yes, when you quench metal parts, if they are not structurally stable, they can warp. Would a barrel warp? Probably not.
 

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you are correct. Aggressive hardening steel also makes it more brittle. But it'd have to get pretty damn hot in order to increase it's hardness properties. "Shooting hot" wouldn't do anything I don't think.
Agreed.
Slowly cooling hot steel softens (aneals) it. Quenching will harden it. BUT, the steel has to be hot enough to enlarge the crystal lattice enough that the carbon molecules can move around. The steel has to be approaching red hot for cooling speed to affect its temper. If you are at all worried, let it air cool for a minute, then dunk it.

ETA: If I needed it cool fast, I would dunk it, BUT I'm chicken so I would hold it vertical and plunge the barrel straight down so it is cooled uniformly side-to-side.
 
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It's highly unlikely you'll get the barrel hot enough to affect the temper. The barrel is likely hardened and tempered similar to hand tools (wrenches, screw drivers, etc) which need to be hard, but need to be more tough than hard (they're only rubbing against copper and lead) That would take about 500-650 degrees to affect the temper.

You might warp the steel though because it's highly unlikely you'll cool the barrel evenly, and if parts cool faster than others, you can lock stresses into the steel and warp it. What's worse, the barrel will tend to relax (unwarp) when it gets hot. This is what causes some barrels to "throw" cold bore shots differently than warm or hot bore shots. So you may well cause the AR to have worse Cold Bore / Hot Bore correleation as well.

razors, scrapers, metal cutting tools and reamers are tempered as low as 350 degrees F. Screw drivers, wrenches, wood saws are tempered up in the 600 degrees range. Structural steel (fully annealled) is 700+ degrees F. Most likely the barrel is tempered in the 550-600 range, so you'd need to get it that hot to affect the temper anyway. Warp on the other hand can occure at much lower temperature.
 
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Looked up a couple of places, and most suggest that carbon steel needs to be 350-500 degrees before it will start to warp if cooled unevently.

If you can put a drop a oil on the barrel and the oil doesn't smoke, you're likely ok. If you can get the oil to smoke, make sure the barrel has lots of time to cool down on its own.
 
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Looked up a couple of places, and most suggest that carbon steel needs to be 350-500 degrees before it will start to warp if cooled unevently.

If you can put a drop a oil on the barrel and the oil doesn't smoke, you're likely ok. If you can get the oil to smoke, make sure the barrel has lots of time to cool down on its own.

The barrel wasn't cherry red or anything, I only put one mag through it a minute or so before hand and it was too hot to touch.
 
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The barrel wasn't cherry red or anything, I only put one mag through it a minute or so before hand and it was too hot to touch.

30rnd in 1 minute isn't going to do anything.

The Pain Threshold (too hot to touch) is 50C about 120F, well below the point that you're worried about what the steel is going to do.
 
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I know cekim, I was refering to the "minutemen" comment. Even back in the mid 1700s, shooting 1 rd / minute wasn't anything special.

For an AR platform, shooting 1 mag in a minute is not going to stress the barrel, even if you dunk it afterwards.
 

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It would have to be pretty frigin hot for it to mater how you cooled it--like glowing red hot.

found online:
As the steel is heated above the critical temperature, about 1335°F (724°C), it undergoes a phase change, recrystallizing as austenite. Continued heating to the hardening temperature, 1450-1500°F (788-843°C) ensures complete conversion to austenite. At this point the steel is no longer magnetic, and its color is cherry-red.
 
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it doesn't need to be glowing to warp the steel or even destroy the temper.

Steel doesn't even glow "Red" in a dark room until it's 750 degree F, and that's hot enough to normalize steel (fully anneal) which will completely remove any heat treatment if it's allowed to cool slowly or nearly fully harden it if it's quenched.

"Orange" heat is 2000 degree F or 1100 degrees C. If you get the barrel to glow orange, it'll be completely useless when it cools.
 
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It would have to be pretty frigin hot for it to mater how you cooled it--like glowing red hot.

found online:
As the steel is heated above the critical temperature, about 1335°F (724°C), it undergoes a phase change, recrystallizing as austenite. Continued heating to the hardening temperature, 1450-1500°F (788-843°C) ensures complete conversion to austenite. At this point the steel is no longer magnetic, and its color is cherry-red.

yes, now look up the temperatures for tempering. "Normalizing" or "Annealing" temperature, which will return steel to its completely unhardened state, is 700 degree F. Annealing the steel will cause it to lose hardness and increase wear.

As for warpage, if the barrel cools faster on one side of the barrel than the other, it will warp upto 1 minute per 43 degrees differential across the barrel.
 
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My logical heart says don't do it.

Ever put a hot glass dish on something cool? SHATTER.

Metal is a different animal but for sure, but I would let it get to room/ambient temperature. If you got loads of money and a handful of ballistics experts at your bidding, then I say do it. [wink]
 
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Steve,

DoD is looking into alternate barrels for the M4 due to some occurances of warpage of the barrel from excessive heat. To my knowledge, they're looking into thicker profiles, alternate materials and fluted barrels. It seems in a sustained fire-fight in a desert enviornment they can heat the barrels up enough to cause problems. 1 Mag a minute? not likely. Feeding 5 or 6 30rd mags through one as fast as you can swap magazines in a gun that can dump a 30rd mag in 2 seconds? That's a whole different beast.

moral: I wouldn't do it and would recommend against it unless you're willing to possible trash the barrel in the process.
 
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Steve,

DoD is looking into alternate barrels for the M4 due to some occurances of warpage of the barrel from excessive heat. To my knowledge, they're looking into thicker profiles, alternate materials and fluted barrels. It seems in a sustained fire-fight in a desert enviornment they can heat the barrels up enough to cause problems. 1 Mag a minute? not likely. Feeding 5 or 6 30rd mags through one as fast as you can swap magazines in a gun that can dump a 30rd mag in 2 seconds? That's a whole different beast.

moral: I wouldn't do it and would recommend against it unless you're willing to possible trash the barrel in the process.
Wear a glove, grow a pair, get a better handguard, get a VFG, etc... [laugh]

I do wonder about the DoD's efforts being more of the overblown "M4 melting" drama from a decade ago? The reality is the competing weapon system (AK) is at least, if not more, sensitive to heat (hand-guards catch on fire and barrel profile is thinner).

Anyway, just let it air-cool. Lock the bolt back, sit down, chat, shoot something else... enjoy the weather...
 
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