Summertime Temps and Barrel heating...

Our shooting benches at the range are under cover (a mandatory thing here in FL, you'd melt without shade), so we're only talking about a minor difference in ambient temperature, 20 or 30 degrees which would be inconsequential.

The real issue is the range is sand, and the mirage can be wicked, even at 100 meters. At 200 meters it can be a big deal.
 
Im with luke on this one. I have never seen much of a change in the size of the groups out of rifles i have shot.Just the way im shooting it.
 
For the barrel the difference in ambient temp between 60 and 100 is not that great. That is especially true compared to the average temp. of exploding propellants.

To your fingers though the difference is pretty big and our fingers don't get exposed to the temp of those expanding gases for comparison.
 
Interesting test on propellant temps on Long Range Pursuit...
Now, this isn't barrel temps- it's ammo.

They tested non temp-sensitive powder (Hodgdon Extreme) against a temp. sensitive one.

They had rounds in the hot sun (120 degrees plus, IIRC), and some in an ice cooler (low 40's, I think).

Chrono'd both batches, at both temp extremes.

The temp-sensitive powder averaged 70 fps variation hot/cold.

Doesn't sound like much, but his point was that for a LR shooter, at 800 yards it meant a 10" deviation in POI.
 
Propellant temperature,

or "prop temp" was always a required data input when calculating artillery fire. It makes a significant difference at long distance (as much as a couple of hundred meters in range @ 8 to 10 miles). Seems it affects the velocity.

So, we required each gun section to keep a thermometer inside one powder cannister, and report the current temp every hour or so.

When you think about rifle prop temp, leaving a round chambered in the action causes the powder to heat/cool to the temperature of the action. So, if you leave the action open, without a round chambered, the powder in your shell will be "air temp", rather than "action temp".

Then, when you think you have allowed the barrel (and action) to cool down enough to return to firing, chamber the round and get off the shots (especially the 2nd, 3rd, etc.) as quickly as you can, to avoid heating the propellant in the shells as they are placed into a warmer and warmer action/chamber.

Also, don't lay your boxes of ammo out in the direct sunlight. The prop temp will escalate quickly under such conditions. Stuffing spare ammo into your pants pockets while hunting will bring the prop temp up to your body temp, too. The result, on a cold day (-45 F), can be considerable. I never tested that theory, and hope I never hunt in anything below about 20 degrees.
 
After it feels really hot, start your car engine with the windows all the way up, and use the air conditioner vents to cool the barrel, with the bolt open for better circulation.
With a MN 91/30 and attached bayonet, it might be awkward. Save the 91/30 bayo for cooking shish kabob. Cook the tiny cherry tomatoes on the oven.

What is unpleasant now is using hearing protectors. They make the temp seem much hotter.
Maybe shooting just a .22 rifle with only protective glasses is best for a while. This is at the river, not the range.
 
I have used and it does really work. I read about using isopropyl, rubbing alcohol, and wiping down the barrel. The evaporative properties of the rubbing alcohol cools much faster than water and is noncorrosive.

I found this to be effective shooting my Mini-14 and Weatherbys here during the summer. I would really soak an old rag, like a rag t-shirt and and wipe down the barrel. The mini barrel would actually sizzle, but after a couple of swipes the barrel was much cooler.

Someone said that the rubbing alcohol fumes were harmful, but I use this outdoors . I use ammonia based CR10 ,and smoke expensive cigars, not to mention reload and shoot for, what most people consider grossly overpowered firearms. I'm don't sweat the rubbing alcohol vapors, and it really works.
 
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