effect of higher temperatures

J

Jim Pollard

Guest
The temperature in Texas goes from the 70 range in early spring to the 95 + range in the summer. Guns that shoot great at 70 degrees become inconsistent as the temperatures start hitting the 90+ range using the same tuner setting and same lot of ammo. That starts me on a hunt to find a new combination of ammo and/or tuner settings to have a "happy gun".
My question is do others hit this problem and what is the solution they have found. I am well aware the air density changes and that could well be the problem. I wanting help or suggestions.
Thanks
Jim Pollard
 
A couple of thoughts...

If I were going to look at what changes as temperature rises, I would first consider lubrication as used on rim fire bullets. I would be very surprised if the cartridges that use wax as lubricant would be consistent. The viscosity of a solid (wax) changes drastically compared to a liquid (oil) as the solid approaches it's melting point. The wax has some advantages over oil such as handling and film strength but I believe it to be less uniform when put through temperature change. You might test brands with different lubes to see if you can find ones that are most consistent.

Second, look at the effect of temperature on YOU. I know I don't perform or do things as well at 95 deg as I do at 70 deg. I know most people consider the fault must lie with the gun or ammo, and every shot that doesn't go in there just isn't their fault, but they might just be kidding themselves. The way rim fires spread their groups it's real easy to miss WHY they do this. Don't overlook the fact the reason your group size or score changes may be because: it's just too damn hot to shoot well!
 
pacecil
Thanks for the come back. We experance temps as high as 105+, so I consider 95 in the shade as not that hot and 70 as cool. I turn on the AC at about 80 degrees.
The wax thing may have some merit. That I will think about it. Would speed of ammo have any affect?
Jim
 
Jim,

We get those sort of temperature ranges here. A lot of the guys keep their ammo in coolers & only bring out wheats needed just before the detail.

Had one guy clean up an ISSF belly shoot a while back when he stuck his ammo on the clubhouse refrigerator to cool it down.

John
 
John
Thans for the suggestion. I had gived the idea of ammo on ice a few thoughts , but never tried it.

Jim
 
Jim,
Icing the ammo down causes it to sweat and get wet pretty quick when you take it out of the cooler. I've seen that happen a few years ago. Just a heads up.

Jim, sent you a PM.
 
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Good question!

Jim,

I have noticed the same effect. I tested my ammo in cooler times and bought a case of the best shooting lot I could find.

Back in the winter I was shooting good for me. I shot my first outdoor 250 at a practice match back last winter. This week in a practice match with the same rifle and bullet combination I shot a 225 and a 230. The wind did not seem to be that much of a factor but everyone was shooting 5 to 15 points below normal.

I can't believe that it is the difference in the temperature of the ammo or the barrel as they both heat up when shot. Can you imagine the effects of the friction on the bullet as it is driven down the barrel at near the speed of sound? I believe that the bullet will leave the barrel much hotter than when you inserted it into the chamber, a few seconds before regardless of the outside temp.

It seems reasonable to consider the change in the density of the air. I vaguely remember something from school to the effect that all gasses expand quite a bit with heat (Boyles Law of gasses or something like that). The effect can be seen in tire pressure as we drive at highway speeds on hot Texas roads. According to this theory air expands and becomes less dense as it heats up. The engineers reading this can check this out but I seem to remember that gas expands something like 1/459 for each degree rise F.

I have heard that airplanes have to go faster in order to take off and land on very hot days. This is very noticeable in hot places like Phoenix in the summer because of thinner air.

If this is the case, Jim, we might need some summer ammo as well as winter ammo or just not shoot in hot weather.

Concho Bill
 
Hi Bill
We both live within about 120 miles of each other and have shot at each others ranges. I think it gets a little hotter at you place.
That said we have the same problem. Things change as it get hotter and scores go down. What can we do about it is my question. Change the tuner, change the speed of ammo, or find a way to chill the ammo down to a temperature of around 70 degrees are my first thoughts. But which is the right one?
Click on my name and send a PM or E mail if you don't want to post. What have you found?
Jim
:):D:)
 
Interesting discussion, How do most shooters store ammo while at the range or a shoot? While I don't have to deal with the temps of Texas any ammo I take to the range is a problem (no roof) Most the time I leave it in the vehicle parked in a shady area. Still a compromise! I currently take mine to the range in one of the small soft coolers no blue ice or cooling products just the cooler for insulation. What temp is in the safe range or I should say a what temp should we start to worry about a (permanent) degrading or a change in the wax? I am in the process of testing ammo and I take all I have to the range with me. Jim P sorry to jump in on your post like this however it was brought up earlier........seemed like a good time to jump in.
 
i have seen people bring their ammo in coolers to keep them from being too hot. What I wonder is how long would a bullet stay in a chamber before it reaches the temperature of the chamber.

I found a site about the speed of sound thru air at different temperatures.
At 55º the speed of sound is 1112 feet per second. Under the same conditions except at 105º the speed of sound is 1168 feet per second. This may not be a factor. I am just stating it for consideration.

Concho Bill
 
Jim Pollard said:
The temperature in Texas goes from the 70 range in early spring to the 95 + range in the summer. Guns that shoot great at 70 degrees become inconsistent as the temperatures start hitting the 90+ range using the same tuner setting and same lot of ammo. That starts me on a hunt to find a new combination of ammo and/or tuner settings to have a "happy gun".
My question is do others hit this problem and what is the solution they have found. I am well aware the air density changes and that could well be the problem. I wanting help or suggestions.
Thanks
Jim Pollard
Click to expand...

Hi Jim how you doing? I recall reading a article about ammo and the season's where it was mentioned having spring and fall ammo and summer ammo. Only thing is if my fuzzy memory serves me right is that it dealt more with humidity than temperatures. If you want to see if possibly the tuner can help try moving it up/down by 5 clicks and see if the grouping is affected. I just can't say from a lot of experinces, but if you have to move the tuner by much I don't think it's going to help. You see a lot of folks state once they find that sweet spot they don't move it. The other choice is to experiment with some ammo. Head out to Dan's and pick a nice hot day and hopefully light winds and see what you can find with ammo. He's got a new lot coming in and unless it all gets sent out should have a nice range to test.

Hopefully the schedule will fall into place where I can make it out to Llano this summer.

Les
 
Hi Les
I am ammo poor--too much on hand I am told by some one at my house.
You are always welcome at at the Llano matches. I have some different speed ammo and plan to do some testing Sat. with lot speeds from 1044 up to some rated at 1075 and not change the tuner.
I got a PM and the idea of humidity was brought up.
Looking forward to shooting with ya
Jim
 
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