Strategy for dealing with temperature

Dave0317

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Mar 22, 2017
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North MS
I’ve seen a few posts about temperature sensitivity.
The usual concern is something like my situation. I live in a state at just above sea level, 95 degree days, and high humidity. My fall hunt will likely be at 9-10,000 feet, around freezing temps, and low humidity. Could be some significant variance in load performance.
Obviously the ideal answer is to develop loads in your hunting weather, or use a very temperature insensitive powder.

With Varget and H4895 being pretty much impossible to find here, I have been using IMR 4895 that I have had for a while. On the shelves, one of the few that stays in stock here is Ramshot Big Game. Neither of these is known for great temperature stability. Load development in my planned hunting AO/weather is not possible either.

So with those considerations, what is the best course of action? Develop a load at the upper end of safe pressures and hope that some decent velocity is maintained when The temperature is 80 degrees lower?
Am I better off buying factory ammo to hunt with?
Am I overthinking this aspect of load deveopment?

Planning on loading 308 with 165 grain bullets (Grand Slams or GameKings).
Shooting out of a 20 inch barrel.
 

nhyrum

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Apr 29, 2019
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Wyoming
Here's what I do. Develop your load in the summer. You'll get the highest pressures then, so no matter what, unless you end up on a star, you'll be safe. Then, track your temperature and MV. Usually in 10 ish degree spreads, and plot a graph. That will get you your mv increase per degree. Apps like the ab app let you input your testing conditions with your mv per degree change. That lets a computer do the math. I think rex in his sniper 101 series goes over how to do it long hand.

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MuleyFever

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I only shoot for load development at dawn. It's the closest I will be to actual temps in the fall. Also per the above suggestion you could get some temp variations for data.
 

hodgeman

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Delta Junction, AK
Serious question- how far are you shooting?

Under typical hunting conditions and ranges, I've never had temperature sensitivity be a factor and I probably hunt a much larger temperature range than most people do. Even with loads developed at 80F, at -30F they still hit within margin of error for POI. I haven't had any issue with factory ammo either, and I have no idea what temp that load was developed at... but they definitely aren't worrying about the temperature sensitivity of their powder.

You'd have to really be shooting way out there for it to be a significant factor. I vote for your #3 choice, I think you're overthinking it.

There's a lot of stuff that will ruin your hunt, I'm thinking that won't be one of them.
 

N2TRKYS

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Alabama
I don’t shoot my hunting rifles in the summer, so I develop my loads during the winter. I’ve never had any issues out West doing it this way, either.

Good luck on your trip.
 

nhyrum

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Wyoming
Serious question- how far are you shooting?

Under typical hunting conditions and ranges, I've never had temperature sensitivity be a factor and I probably hunt a much larger temperature range than most people do. Even with loads developed at 80F, at -30F they still hit within margin of error for POI. I haven't had any issue with factory ammo either, and I have no idea what temp that load was developed at... but they definitely aren't worrying about the temperature sensitivity of their powder.

You'd have to really be shooting way out there for it to be a significant factor. I vote for your #3 choice, I think you're overthinking it.

There's a lot of stuff that will ruin your hunt, I'm thinking that won't be one of them.
True. You really only need minute of elk accuracy not 600 yard clovers.

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Cahunter805

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Oct 8, 2012
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If you want to test your loads you can put 3-4 rounds in a double plastic bag and into a cooler with some Ice for a few minutes then chrony and see what velocity is when cold. Like stated above it probably won’t be a factor unless you plan on shooting long range. Under 400 it shouldn’t be a problem.
 
OP
Dave0317

Dave0317

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Mar 22, 2017
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North MS
Cool. For my hunting purposes it definitely won’t be an issue then it sounds like. I do plenty of long range shooting, but with all factory ammo. I’m just now starting to get serious about reloading and I wanted to start with my hunting rifles.

So I think I really tend to analyze every factor like I’m prepping for a long range match. When you put it all in perspective, my hunting requirements are super simple. I’m not bringing my long range gun (KMW Sentinel) on the hunt. I’ll bring a Model Seven in .308.

I really plan on limiting my shots with the Model Seven to 300 yards. So it sounds like if I lose a good chunk of velocity, I’m not going to be able to blame a miss on that. Lol.

Do y’all usually check your zero at your hunting location? I suppose at least that may give me a bit more confidence once I’m at higher elevation and in some cooler weather.
 

nhyrum

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I just take it out in the general conditions its going to be a little before I actually go and make sure it's at least close

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Rob5589

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W Sac CA
I wouldn't worry too much about it for hunting. You can run some data through JBM to give you an idea of the differences.
 

wyosam

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Aug 5, 2019
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Just shoot to confirm when you get there. It will be cooler, but the air will also be thinner. If you’re planning on keeping it to 300 or so, I’d start with 1 cold bore shot at 300. Hopefully that tells you everything you need to know.


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tdot

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BC
During load development, I typically look for wide accuracy nodes, during cooler times of the day Spring/Summer, not just the fastest load I can safely shoot. Then I load at the top end of the accuracy node. This way, even when I lose velocity due to a temp drop, I'm often still within the Accuracy node and rarely notice any significant difference in accuracy, even during range days in the middle of winter.
 

Clucknmoan

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Sep 30, 2018
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First of all make sure you are using a temp stable powder, like H Extremes.
When you are developing your load, don’t just find a single powder charge that shoots. Look for an entire node that shoots well and consistent over a fairly wide powder charge range. Depends on case capacity, but a .223 might only have a node that is .5 grains wide, a 300 RUM might have one 1.5 grains wide. Shoot over a good chronograph to initially find the nodes and then shoot ladders at long range to narrow them down. Lot more to it than that, but that’s the short version. Once you know the exact powder charges where your node starts and stops, Load right square in the middle of it. Or, shoot the low side of the node in the summer and shoot the high side in the winter.
 

Clucknmoan

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Oh, and don’t bother doing much with this until you have at least 100 rounds down e barrel and have your brass fire formed. It will likely all change after the barrel is broke in and you are running fired brass.
 

Laramie

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Apr 17, 2020
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Good advice above. For POI, I recommend arriving a day early and shooting. Going from warm low elevation, high humidity, my zero is approximately 45 yards different at elevation in cool weather. I sight in this way intentionally (205yrds = 250ypds) as I use a B&C reticle. My cross hairs then become 250, 350, 450, etc. at elevation. I'm shooting a 30-06 with 165 grain bullets at 2900 fps.
 
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