Hey guys just thought I'd post this due to several E-mails I got asking for the same thing (I will return the E-mails)
the rig I use is setup to flush cool water/alcohol down the barrel from the chamber end.
1) your going to need a squeeze bottle that you can make a
hole in the lid for a piece of small tygon tubing to fit
2) you need a couple feet of tygon tubing 1/4"-3/8"
3) a small piece of steel,copper or any other ridgid tubing
that will fit snugly into the tygon tubing about 12"
4) one of those plastic chamber plugs with the o-ring that
is used to seal off your barrel so it can be filled with
Now take the chamber plug and drill a hole through it from the back to front the hole needs to be sized so that the piece of metal tubing can be threaded or glued into the back of it ( I tap mine)
then screw or glue the tubing into the back of the chamber plug so that it can be run through the back of the action to plug the barrel off.
attach the tygon tubing to the back of the metal tubing so that it won't come off when some pressure is applyed
now fix the tygon tubing to the bottle so it will squirt out when you squeez the bottle (I like the sports drink bottles that have the straw that uns down through the lid)
so now you should have a water bottle that has tube running to a chamber plug lolly pop., so when it time to cool the barrel you pull the bolt and run the plug into the chamber and flush your coolant through it.
I hold my gun on the bags at a slight angle so that the barrel fills before it runs out the end , you'll want to wrap a rag around the muzzel so that the fluid doesen't run back down toward the stock
I use a 50/50 mix of rubbing alcohol and water as my coolant.
Edge , I forgot to mention that the water I use is distiled
I use the 50/50 mix because its cheaper and makes it last a little longer.
Acetone actualy works realy well but it isin't exactly the stuff you want running all over the place or your gun for that matter.
their are several way you can make this setup work , the first ones I make I just used a tapered rubber plug with a hole drilled through it and that worked realy well but the plugs got hard to find and somtimes came off in the chamber making a mess on the bench
The Possum Hollow chamber plugs work well because they are steel and can be tapped.
I generaly just run a couple dry cotton patches through the bore before the next string of shots. I have also used cool damp rags to cover the barrel when shooting more than 3 shots like when varminting.
I also like to have a pretty big gap arounbf my barrels when they are free floated to allow a little more air to get around the barrel , some of my varmint guns had a 1/4" gap around the stock and had cooling vents cut into the bottom and sides of the stock.
Rob01 , if your getting your barrel so hot that you can warp it buy cooling quickley then it isn't gonna last anyhow .
Typicaly your barrel isin't going to get much hotter than 125 to 150 degrees which is a bit hotter than you want to touch for more than a second or so , if you shooting it to the point that its in the 300 degree range that might start to have an effect on the barrel steel so as it might warp then your shoot way to many times between cooling it off.
I have shot out around Barsto , CA when it was 110 degrees. I was shooting a 300Win mag with a fluted varmint weight barrel , I would cover the barrel with damp rags and shoot 5 shot groups , the barrel would be warm but no where near as hot as it would be if I had just left it out in the sun.
At some point you have relize that if your not at least keeping the gun in the shade then it ain't never gonna cool off.
But answer your question , no I have never been worried about warping a barrel from cooling it to fast , I don't worry because it not getting that hot and the water isin't ice cold.
I have a buddy that has this same setup I mentioned but it is fed from a small pump into a 6 to 1 header ,he has 6 differant setups so he can be cooling 6 guns at once , this insures that his guns are staying cool while he is shooting at the range. Its a pretty cool dealas it recycles into an ice chest that its being fed from .
Here are some suggestions to maybe make your setup a bit easier and less messy (food for thought). You can install these Cap Fittings on a windshield washer solution jug. Then use the hand crank fuel pump to go from jug to the end of the barrel (you would have to plug the end of the barrel), pump out toward the chamber, disconnect the exit line and reverse pump to suck out the remaining solution. This stuff was designed for model airplanes to keep your fuel in a semi enclosed system (to keep fuel moisture free).
These pumps will move a lot of fluid with little cranking. They also make electric models and if you wanted you could use 100% rubbing alcohol.
Why make things so much more complicated than they have to be? I cool my barrels down quite rapidly (and inexpensively I might add) by simply draping a damp dish towel over the barrel. Works quite well. Heck, I sometimes even shoot with it draped over the barrel and it doesn't effect accuracy or POI at all that I can tell. But it sure helps keep the barrel cooled down.