Cooling a barrel with a wet rag

[falldowngoboom]

I was at the range yesterday testing loads. Weather was 100 degrees, so I used a wet rag wrapped around my barrel every six shots or so to cool it down as it was getting really hot (fry an egg hot).

The guy next to me said that I should let the barrel cool naturally and that using the rag might warp the barrel, particularly because I couldn't put the rag over the side of the barrel covered up by the stock.

I've read some posts here, mostly saying that using a wet rag is probably okay, but does anyone have any references where actual testing has been done to see how quickly you can cool a barrel without permanently affecting accuracy?

I've been thinking about getting a small battery operated fan to clip on and point up the muzzle as an alternative.

 

[Zak Smith]

I wouldn't douse it with cold water, but I've used warm water evaporating to cool a barrel before. A fan blowing air through the barrel would probably work better.

 

[DMK]

If you stand a rifle upright with the bolt open, the chimney effect will pull air into the breach and up the bore (heat rises, creating a slight vacuum in its wake). If you could somehow provide cooler air at the area of the breach, that would help.

 

[Maverick223]

I wouldn't put a wet rag on most rifles (with exception of something like an AK), but I doubt that it would hurt anything.

I think you just came up with the newest tacti-cool (pun intended ) accessory...the picatinny rail mounted cooling fan.

 

[rcmodel]

Or a Molle vest A/C system with a quick-couple barrel plug.

Or a barrel with a water jacket like an old Browning machinegun.

rc

 

[falldowngoboom]

Will get the R&D team right on it! Thanks for the replies guys.

 

[Slamfire]

The guy next to me said that I should let the barrel cool naturally and that using the rag might warp the barrel, particularly because I couldn't put the rag over the side of the barrel covered up by the stock

I doubt this. Your barrel is not being heated anywhere annealing temperatures. At most it might be 300 degrees. You are not heating the barrel to cherry red, and are not bending or forging the thing to a new shape.

This is an non steady state heat transport phenoma, which means you would need to model it to exactly determine just how fast heat moves in a metal. And I am not going to attempt this. But at temperatures below wood char level, I think the concerns are unfounded.

 

[Uncle Mike]

Co2 Fire extinguisher, works great. make an adapter to go in the breech end, like an old cartridge, slip it in and give it a blast or two.

Burrrrr!

 

[NC-Mike]

Unless you're shooting off long strings of rapid fire, I wouldn't worry about it.

Certainly not 6 rounds. That's nothing.

 

[groundhog34]

I don't know about a wet rag but my rifles get hot after 5 to 7 rounds and accuracy goes to hell. Groups go from 1.5 inch to 8 inch, all over the paper especially with my Weatherby. Must be the light barrel.

 

[rockstar.esq]

Slam fire is right to a point. High carbon knives are tempered at around 350 (black heat) which wouldn't necessarily burn the wood but it would be getting mighty close. Annealing is simply tempering taken as slowly as possible. Quenching the steel would do more for keeping the steel hard than letting it cool slowly. From what I understand barrels are made of medium carbon steel. As such it would stand to reason they have less potential to work harden from rapid heating and cooling. Since toughness is what a barrel maker would be looking for it would stand to reason they aren't particularly hard to begin with. I suspect it wouldn't do any real harm but I've yet to meet a shooter who didn't believe in metallurgical voodoo when it comes to barrels.

 

[Jeremy2171]

Had only the one barrel for an M240 MG and had a bunch of rounds to shoot.... every 200 rounds pull the barrel and poured a bottle of water through to cool it..initialy it spit steam right back at but if you pour slowly 1 bottle will cool it off quite a bit. We kept this up quite a bit until we used up the ammo.

 

[Slamfire]

I don't know about a wet rag but my rifles get hot after 5 to 7 rounds and accuracy goes to hell. Groups go from 1.5 inch to 8 inch, all over the paper especially with my Weatherby. Must be the light barrel

.

I suspect that light barrel was "straightened" or maybe the blank that it was turned from had internal stresses. It is well known that light barrels are most suspectible to walking.

I have a almost new M1896 that walks. The sucker will change its elevation at least 8 MOA as the barrel heats up.

I keep on telling myself that I am going to have that barrel cryo heat treated.

The Iraqi vet reminded me of something. I have a bunch of awful Iraqi 303 ball. I decided to shoot up as much as I could one day. I shot my SMELLY as fast as possible, until the forend metals parts were so hot they were really unpleasant to touch.

Then I opened the bolt and poured water down the barrel. The barrel was so hot that it vaporized the water, and blew the first pour out like a geyser. However the barrel cooled fast enough with subsequent treatments.

Since the barrel was pitted, I have no idea if the accuracy was affected.

 

[Redneck with a 40]

My heavy barrel Remington 700 SPS Tac in .308 can fire 30 rounds at a normal pace, without getting overly hot. I let it cool about 10 minutes after a 30 round string, but it never gets too hot to touch. I like heavy barrels.

 

[dubbleA]

I use a small blower, 100 degrees days are the norm in S Texas in the summer. I load in 5 rd increments, the barrel is cooling while I load another 5 rds. Works like a champ.

 

[JDGray]

dubbleA, Nice setup you have there! Is that your garage your shooting out of?

How do you like that new Choate stock? Wish that one was available when I bought my Choate UV stock for my 10FP.

 

[Maverick223]

I would avoid pouring water down a hot barrel, because if I remember my Hydraulics correctly cavitation could occur when the pressure of the water vapor meets the cooler water being poured in from the top (whether the chamber or the muzzle). This phenomena *could* damage a barrel as it is a fairly violent reaction, I am not sure that it would cause harm is a gun barrel, but I would avoid doing so in my rifle.

 

[Big_E]

I usually try to use compressed air (half the time I forget to take it w/ me) but here in the SJ Valley, it doesn't really matter because in the heat just leaving a rifle sitting on the stand will heat up the barrel.

 

[Uncle Mike]

I'm tellin; ya...a co2 fire extinguisher!

 

[Marlin 45 carbine]

when I rapid-fire my Mini30 it really heats up, 2 20 rd mags dumped and it's getting hot.
it's not a 'spray for effect' gun so I don't need to burn the rifleing out of it.
when testing handloads I have took ice cubes from my cooler and rubbed the barrel to cool it back down.

 

[MCMXI]

The guy next to me said that I should let the barrel cool naturally and that using the rag might warp the barrel, particularly because I couldn't put the rag over the side of the barrel covered up by the stock.

I don't think his comment had anything to do with annealing. He's referring to the problem of uneven cooling. The coefficient of thermal expansion (CTE) for typical alloy steels is somewhere between 6x10^-6 and 9x10^-6 in./in.°F. So for the worst case scenario, a 26" barrel will increase in length over 80°F to 300°F accordingly:

80°F to 100°F = 0.0047"
80°F to 200°F = 0.0281"
80°F to 300°F = 0.0515"

A barrel that increases by 0.0515" over its 26" length experiences close to 60,000 psi of internal stress (based on the strain and an E of 30,000.000 psi). If the barrel heats up and cools down uniformly, the internal stresses are much more likely to be uniform. If a barrel is suddenly cooled along one surface, the internal stresses will no longer be uniform and the resultant uneven internal stresses may have unexpected/unwanted results.

My thinking is that it's better to let the barrel cool uniformly so I don't put wet rags on the barrel. I will admit that I don't know if cooling with wet rags or a towel will cause damage to the barrel, but I'd rather not take the risk since I haven't conducted any tests using strain gauges or the like. If someone does conduct some tests that prove empirically that uneven cooling has no deleterious effects then I'd certainly consider bringing a towel and a gallon of water to the range. In the absence of such data, I'll fall back on my limited knowledge of stress/strain curves and CTEs for steel alloys.

 

[Joe Demko]

Why don't we get more posts like 1858's at THR?

 

[Al Thompson]

IIRC, a few years back Precision Shooting showcased somebodies barrel cooling rig. Not sure if it went commercial, but (again IIRC) it was a compressed air or nitrogen device that blew air down the barrel.

 

[Bruno2]

a wet rag thats how they straighten bent driveshafts . I wouldnt do it . I have always been told when a barrel gets hot to the touch it needs to cool .

 

[Maverick223]

Good info 1858. It is nice to be able to put an empirical value to my thoughts and ramblings. What are your thoughts on pouring water down the bbl? I wouldn't do it, but am not sure what damage would occur if any.