Cooling Barrels

[Ovidio]

The most annoying thing at the range for me, especially with milsurps, is when the barrel gets hot and forces you to change rifle or stop for a good while.
I always wanted to buy something to help cool down the barrel, but I had no ideas and didn’t want to pay a lot of money for those flimsy ventilators you can find in gun shops. 50 bucks for a piece of plastic…plus shipping cost.
A few weeks ago, while looking for a solution, I stumbled upon a video from a really nice Italian guy and found his idea interesting: a usb powered portable pc fan.
Found them on the Internet and bought the one which looked right. Approximately 51x51 mm and 15 mm thick.
It was sold only in couples, so I had to invest more than that guy…6.50 €, shipping cost included.
Yesterday I tried them out with my Persian Mauser and P14.
WONDERFUL!

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[RCS]

My Winchester Hi-Wall rifle, mix-master of parts: coil spring hammer, original double set-triggers, Darr heavy barrel 1 3/4 inch across flats, breech loader in 32-40 Winchester. Bullet from special Hoch nose pour mold is breech seated into barrel rifling then case is chambered and fired. Never heats up.Attachment 120884Attachment 120885Attachment 120886

[CINDERS]

Awww! come on Ovidio don't tell us your that cheap!
You must fuel them, the only time mine get super hot is in the mad minute my best was 25 rounds/200m even with a rim over that had to be sorted, picked up the $50 kitty with that one, but boy the heat was there alright after that effort, for normal slow fire though the barrels though warmish are not like a hot plate...

Good idea though.

[Ovidio]

I'll think about a short extension to make that thing fit better yet into the rifle's chambers.
It sorted the problem of the mirage in a matter of a few minutes.

[ssgross]

The other year I was considering such a solution to quicken my wait between groups. I read an article (was it from pew-pew? can't seem to find it, wait here it is...https://rifleshooter.com/2017/08/do-...-coolers-work/) where they guy did some tests. Summary...Empirically, it seems blowing room temperature air down a bore is minimal help at best. Some more reasons why?
Treating the volume of barrel metal as a constant...the heat radiated as a barrel cools should be directly proportional to the surface area - the Stefan-Boltzman equation is the one we want, I think, The surface area inside a 22inch .308 barrel is about 21.01 sq. inches. We can use the average outer diameter since a tapered barrel is like a frustum... maybe 1 inche? (need to measure some barrels) the outer surface area is 69.1 sq. inches. So, the inside of the barrel accounts for only 23% of the total surface area of the barrel, maybe a bit more for a pencil barrel, and less for a bull or varmint barrel. So, we would be much more effective popping off the handgaurd and putting a fan on outside.

The mirage being eliminated early is likely because the rate at which heat is lost slows with time...e.g. most of the energy loss happens early on, and 3/4 of the heat loss is from the outside - which creates the mirage to begin with. Try sticking a thermometer in a cup of coffee and taking a reading ever minute. Big temp. change in the first 10 minutes, not so big a change after 30 minutes.

Now suppose it's time for the internet experts who spent big money on their custom chambered coolers to troll my math oh well.

[Mk VII]

A brass rod of the right diameter would bleed more of the heat out of a barrel.