Temp Sensitivity

[Gomer]

I will be in the Eastern Cape in August of 2027. Google says average highs of 72 and lows of 48. Where I live, I typically develop loads in the summer where temps are usually around 80 (at sea level). If that’s the case, I should be good if I settle on a load thats under max pressure here, right?

 

[KEC]

Yes Sir!

 

[matt85]

Most modern powders are pretty stable. You can find charts online for which powders are more sensitive.

 

[Gomer]

Most modern powders are pretty stable. You can find charts online for which powders are more sensitive.

What I am trying to do is eliminate temp sensitivity as a factor. The way I see it I either pick a temp stable powder and hope it’s best for my rifle, or develop a load at similar average temperature and use whatever powder that shoots best regardless of its temperature sensitivity. I’m more concerned with pressure.

The problem is, if I develop a load in July here, I have 3 months of practice time with that particular load if I am hunting at home. If I do the same next year, I will have a month before my trip. Currently, I’m practicing with cheap bullets of the same weight that I don’t intend to take with me.

 

[KEC]

There always seems to be a few powders that stand out in each cartridge for accuracy and performance. I will usually start with one of these powders that is the least temperature sensitive. Example: .308 win- H4895, Imr 4895 or Varget, I would try the H4895 or Varget first depending on velocity and pressure.

 

[matt85]

Unless your dancing on the max pressure line. The most sensitive powder available today will still be stable enough to be safe.

More likely, a temp sensitive powder could cause a POI shift or a reduction in accuracy.

 

[Russ16]

The temp differences you’re referencing aren’t enough to worry about.

 

[45-70guy]

You should be fine,
I used cfe223 which if you go by the “data” should be very UNSTABLE.
Loaded and tested a ton of rounds and by tons I mean a few 100. From temps In the 20’s to temps in the 80’s.

If you deep dive into temperature affecting powder especially in a hunting situation it seems once you get over a temp of around 100 or so then the swings really show.

 

[Gomer]

You should be fine,
I used cfe223 which if you go by the “data” should be very UNSTABLE.
Loaded and tested a ton of rounds and by tons I mean a few 100. From temps In the 20’s to temps in the 80’s.

If you deep dive into temperature affecting powder especially in a hunting situation it seems once you get over a temp of around 100 or so then the swings really show.

The temps where I live don’t fluctuate much at all. It maybe gets into the low 30s a couple weeks worth of days a year. Same number of days over 85. With 30-06/H4350/180gr jacketed bullets, I get 2825 in the heat of summer and 2775 in the coldest part of winter.

 

[Wildwillalaska]

You should be totally fine. I just took some loads with RL15 for my 500NE that I developed in May when 45-60 degrees, used during the summer when we’d see 70, and took to northwest Zimbabwe for most of October where we saw high temps several days between 112-116. Performed flawlessly…but also wasn’t loaded to max pressure. I did the same with my 450NE last year. Don’t push the envelope if temps will be higher, and of course can nudge closer if temps lower…but Africa seems a lot like my home here in Alaska. If you don’t like the weather, wait 15min.

I am also trying to lean into more temp stable powders for my doubles, like I do for my Alaskan hunting rifles where I may shoot at 75 degrees or 10 degrees and everything in between.

 

[Charlie64]

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I think you are over analysing this one. Same loads you are using at home will work just fine all over RSA, whether Limpopo or the Cape.

Cheers

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[Gomer]

.

I think you are over analysing this one. Same loads you are using at home will work just fine all over RSA, whether Limpopo or the Cape.

Cheers

.

.

You should see how many pairs of boots I bought.

 

[steve white]

And this is yet another endorsement for sighting in in Africa, as your PH will surely have you do, anyway. You will then know exactly where it hits in Africa no matter what it did back home, so I wouldn't sweat it. There are lots of more interesting ways to miss, anyway, lol.

 

[KEC]

You should see how many pairs of boots I bought.

We're alike with over analyzing, sometimes I lose sleep over it.
I tell myself I'm normal, but my wife just doesn't understand.

 

[Mark A Ouellette]

As all the other members stated, unless you load to the maximum pressure in 48 degree weather and then shoot at long range in Africa at 80 degrees, you will not notice a difference in point of impact with almost any powder.

Attached is a Powder Burn Rate with Temperature Sensitivities listed.
The powers at the top of the chart are the fastest buring.
The column to the right of each powder is the increase in projectile velocity per 1-degree increase in temperature.

To compare,
- IMR 4895 increases 1.1 fps per 1-degree increase in temperature
- H4895 increases .23 fps per 1-degree increase in temperature

For your 32-degree change in temperature from 48 to 80 degrees,
- IMR 4895 will develop 35.2increase in velocity
- H4895 will develop 7.36 increase in velocity

I don't know what the increase in pressure would be but if you would develop loads at 48 degrees and then hunt Africa at 110 degrees the effect will double in velocity and you might find a stuck bolt when you might most need a rapid second shot!

 

[deewayne2003]

I’ve used RL22 for over twenty years now in calibers from .257Wby - .416Rigby and as said by @Mark A Ouellette; do your load development in similar temp or higher and you’ll be good.

I would develop loads in 90+ temps and have hunted with it in temps ranging from 10F-105F and had zero issues, in fact I’ve hunted with the same 100rnd lot of 300win 200gr Partition RL22 load for everything from Canadian moose to African plains game.

When that ammo ran low it was time to develop a .300win do all travel load I went with H4831sc again at the suggestion of @Mark A Ouellette to avoid the issue entirely and get the most out of case capacity for 200gr LRX.

 

[45-70guy]

The temps where I live don’t fluctuate much at all. It maybe gets into the low 30s a couple weeks worth of days a year. Same number of days over 85. With 30-06/H4350/180gr jacketed bullets, I get 2825 in the heat of summer and 2775 in the coldest part of winter.

Yea if you do ballistics calculations on all sorts of changes like velocity, temp, elevation, you will see out to 300 yards almost none of it matters so long as your in the middle of the range of spec.

 

[C.W. Richter]

Agree with everything printed above. IMR (my fav) powders are temp sensitive, but not when going from a warmer climate to a cooler one! It's an issue for me living in the Appalachians heading to TX or Africa (but I typically find that backing off 0.5 gr on hot handloads does the trick-and it prints the same in country. Now, be more concerned about elevation differences when heading to Africa. You'd be surprised how many places are at higher elevation than Denver! On one trip to Namibia, everything was printing 4"+ high, but there are actually places in RSA/Namib/Zim that are 8,500-11,000 ft above sea level (and that has more pronounced effects on your sight-ins!!!) Many hunting areas are 4,500-6,500.

 

[coreydb]

I ran into that issue myself. I'm just glad I got to re-zero my rifle on site at the lodge. There definitely was a difference with POI.