I know that powders are affected by temps. Some more than others. It is clear to me that the velocity of a load developed at warm temps will be less than at cold temps. What is not clear to me is how accuracy is affected by temps. (loss in velocity). Lets say I work up a load for gun A in 85 degs, with 71 gr of powder and 3000fsp I get MOA. With the same gun, brass bullet powder, temps etc. and 69 gr of powder I get 2900fsp and 2.5 inch groups. Now it's hunting time and the temp is 10 deg. The load with 71gr of powder now has a velocity of 2900fsp. Do I now have a MOA load that is just slower or do I have a load that shoots 2.5 inch groups? I guess what I am asking is, with the loss in velocity is accuracy also lost. I know that POI will change but what about MOA?

For the size of deer you have in Minnesota you need all the accuracy you can get.....I've shot bigger mice here!!!

However the temp has never caused me accuracy issues or changes that I've ever noticed...

Vapodog, The deer here in the far northern part of the state are even smaller than the deer in the southern part. We have wolves and some pretty harsh winters. The deer also get hammered during the hunting season. Most of the deer hunters here shoot anything that comes their way, big or small. Still, our camp gets one or two 200+ pounders each year. Nothing like the monsters of Nebraska, but not to bad.

[IMG] [/IMG]

Steve
Use a powder that is temperature neutral, say 4895?

What caliber are you shooting?

Halvey
From southern Minnesota, where the deer are big, and the women bigger.

quote:

Originally posted by steve4102:
I know that powders are affected by temps. Some more than others. It is clear to me that the velocity of a load developed at warm temps will be less than at cold temps. What is not clear to me is how accuracy is affected by temps. (loss in velocity).

Hi Steve,

I am tickled at some threads where the shooter says: "Haven't tried the load yet as weather is too cold, or snowing," etc, etc.
I test all year round and we see real COLD nestled in the northern Rockies. Wind is about all that stops me. I've shot 1/4" groups at 100 yards with it snowing so hard I've had to wait for a slight lull to get a good sight picture. Never could figure out why snow won't deflect a fast .22; but I've shot too many good groups to think it does.
But to your question. There isn't a textbook answer. Like a different velocity may shoot better faster or slower due to harmonics, pressures, or whatever; the same can happen when your ammo gets cold. If I was to summarize my experience I would say usually cold is more accurate if you CONTROL all the other things that the cold brings into the picture..
Things like keeping a uniform barrel temperature for shooting groups. A barrel barely warm to the touch will put heat waves galore into your scope at 15 below zero! I also keep the shells for my group in an inside pocket to try and keep them a uniform temp for the five shots.
I have shot groups with the gun and ammo almost dry ice cold letting the gun cool several minutes between shots back to where your tongue would stick to the barrel just to see how the cold weather groups are;....but even more so to see point of impact change, if any, for a cold weather hunt with cold gun and cold ammo for that critical first shot.
Put on your Carhartt's and get out and do it will answer the correct answer for your combination, as all guns are different as well as the loads. Just know it is GUN and LOAD you are dealing with in extreme cold and the hiped up (cold or hot) powders may help the cartridge but you still have the effects of cold on the gun as well. Even the shooter's ability is a variable between warm and cold, maybe, unless you are Norwegian!

BigRx

quote:

Originally posted by steve4102:
Vapodog, The deer here in the far northern part of the state are even smaller than the deer in the southern part. We have wolves and some pretty harsh winters. The deer also get hammered during the hunting season. Most of the deer hunters here shoot anything that comes their way, big or small. Still, our camp gets one or two 200+ pounders each year. Nothing like the monsters of Nebraska, but not to bad.

[IMG] [/IMG]

I was shitting you of course.....I've taken some monsters around the Tofte/Grand Marais area!!!

quote:

Steve
Use a powder that is temperature neutral, say 4895?

What caliber are you shooting

300WSM with Ramshot Hunter
7MM-08 with Ramshot BigGame
30-06 with Ramshot Hunter
7.62X39 with AA2230
The reason I asked this question is, I here so much about temp sensitive powders this and sensative powders that. Most of what I read is about change in velocity, some say no big deal some say it is a big deal to lose 100+ fps. Velocity matters little to me compared to accuracy, but, if that loss in velocity degrades accuracy then its time to change powders. I guess I need to do a bunch of testing and see what my "perfect loads" do.

quote:

Even the shooter's ability is a variable between warm and cold, maybe, unless you are Norwegian!

Yes sir, But, I still get my ass froze off up here.

Hello,
Research by military will tell you that w/ approx. 20F change in ambient temp. as much as 1 moa can be realized. Start shooting in AM, temp. 65 F and then in the afternoon, temp is over 90 F you could have noticeable increase in velocity. You learn to keep your ammo covered and protected from the temp. as much as possible. Rounds will "climb" on you, but have not experienced less accuracy, just different POI.
Varget is regarded as one of the most temperature stable commercial powders available to civilians and it is very versatile in a lot of calibers. Many Palma Match shooters use the Varget powder due to it's stability in broad temperature swings plus it works very well indeed in the 308 round.
Favor Center!!
dsiteman

I've only seriously tested one load for cold and warm temps. My 220Swift loaded with IMR4064 will shoot groups in the .3-.4" range down to 10 degrees. At zero groups are about .6-.75". The rifle also wears a synthetic stock and I'm not sure that it doesn't do wierd things in the cold.