Reloading especially for African temperatures?

[Bonde]

I wonder how big the difference in chamber pressure will be between temperate northern 15C and upper dry Zambezi Valley at 40C?

Using either IMR4831, Relaoder 15 or Vihtavouri N165 in a .450/.400 3» in an old double rifle.

Neglectable, or knock off a grain or two?

 

[ChrisG]

I would say with modern powders, loading a 450-400 to it's original specs with modern bullets. You have no worries. I believe the original Nitro cartridges were only loaded to like 40,000 PSI so no worries there. Modern powders are also a whole lot more temperature stable than cordite was.

 

[Ray B]

Thirty-some years ago a friend did some bullet testing with a 375/8mmMag using a few powders, but mainly H4831. the loads were right at the top of his rifles maximum loads. during the course of the testing, one day (in Northern Idaho) was 80+F and sunny. Most of the ammo was in the shade but a few boxes were exposed to direct sunlight. when it came time to shoot the ones that had been in the sun there were immediate signs of higher than good pressure. Primarily, brass swaged into the ejector slot which the bolt shaved, leaving a very bright spot on the casehead. Those boxes were heldover for a cooler/shady day and performed back at the usual no extreme signs. the conclusion was that the H4831 was susceptible to temperature related variations. Since those days in the early 80's Hodgdon has introduced powders, including H4831 that are listed as temperature "Extreme" and is advertised as being affected very little by variations in temperature. I know of no independent testing of side-by-side loads using the old and new powders to show a comparison, or independent testing to show how cartridges perform when allowed to sit in the sun for a couple hours.

But as noted previously, if the 450/400 is loaded to original performance an increase in pressures due to temperature should still be well within the safe limits for the cartridge/rifle.

 

[Divernhunter]

You will be fine. Do not worry or change the load.

 

[Nyati]

I have heard about Vihtavouri being temperature sensitive.

 

[crs]

I have used VV N133 here in Texas for years and have never noticed any temperature issues.
Of course, I do not go off and leave a loaded gun or box of ammo out in the sun either. This includes not leaving ammo on the dash board or bed of pickup truck in 100+ degree weather(or cameras, cell phones, most plastic, etc.).

The warmest September dove hunt that I remember was 110 degrees air temp in the shade - not asphalt road temp.

 

[zephyr]

If you stick with the Temp in-sensative powders you should be fine. I have been switching over to the Hodgdon Powders H4831 and H4350 will get you where you want to go

 

[gatekeeper]

I have spoken with John Barsness, who has done testing with several of the temperature insensitive powders, and stated they have shown very little variation to temperature change. He recently tested RL 16 and RL 23, and said they did very well. RL 26 is not listed as being temperature stable, but John said even that did well for him too.

 

[Dr Ray]

I would say with modern powders, loading a 450-400 to it's original specs with modern bullets. You have no worries. I believe the original Nitro cartridges were only loaded to like 40,000 PSI so no worries there. Modern powders are also a whole lot more temperature stable than cordite was.

Agree.

 

[fourfive8]

Probably no issue if sticking to older, more conservative ballistics. But 40C or 104F temp is hot and if gun is sitting in the sun it will get MUCH hotter. I'm sold on temp insensitive powders like the OZ powders Hodgdon sells in their "extreme" line. Given the cost of an African trip and the todo about expensive double rifles and all that goes into one of these hunts and the animals involved seems false economy to piddle around with ammo. If you reload, no reason not to at least try some possibilities with one or more of the known temperature insensitive powders in addition to trying some slightly reduced pressure loads no matter the powder.

 

[Bullthrower338]

I am about to give some IMR 7977 a try in my 470 NE, it is one of there enduron line of powders which are temp insensitive. If it is as good as all the reports I’ve been reading it might be a good one to look at also. @tarbe might offer some good information as he has been developing 450/400 loads as of late.

 

[tarbe]

I wonder how big the difference in chamber pressure will be between temperate northern 15C and upper dry Zambezi Valley at 40C?

Using either IMR4831, Relaoder 15 or Vihtavouri N165 in a .450/.400 3» in an old double rifle.

Neglectable, or knock off a grain or two?

Load 78gr of IMR 4831 with a 400gr Swift or Woodleigh and forget about the temps (assuming this load regulates ok for you...it should give you around 2,050fps give or take, depending on your throat and bore dimensions and which bullet you pick). 78gr is my standard plinking/practice load but runs about the same speed as the Hornady factory ammo (actually up to 50fps faster).

If you know you are going to be hunting at or near 40C, is there any way for you to do your load development at temps higher than 15C? I always try to develop my hunting loads at temps close to what I will see when hunting. Just seems prudent.


Tim

 

[Vanguard2279]

While this is real science-based, I attempt to develop loads in the temperature that I will be hunting. Given that I live in Vegas, I have plenty of hot weather. Ther most accurate load out of my .338-06 is a 210-grain Barnes TTSX backed by 63 grains of H414. I literally shot a one hole group at 100 yards. The velocity was a bit over 2,800 fps, but I was experiencing sticky bolt lift. I reduced my load to 62 grains of H414 which still shot into an inch consistently and gave an average of 2,775 fps. This functioned fine in April heat in northeastern Namibia. I'll test it again in the lovely 110 degree heat in early July.
One advantage in developing loads in slightly warmer temps when it will be used in colder is that if it's safe in the heat it will be fine in the cold. Unfortunately, the colder weather could affect velocity and accuracy.

 

[Vanguard2279]

That should say "While this NOT real science-based,..." Sorry. My bad. I've had a few typos lately. See my latest hunt report.

 

[Rule 303]

40C is hot but not overly hot and most modern powders should be OK if kept out of the sun, though I would drop a grain or two from non temp stable powders. Why, 40C is temp in the shade, temp in the sun can be 50C or a bit more and hotter inside the case. This will make a definite difference-in my experience- with non temp stable powders.

Not saying you will put rounds in the sun deliberately but just on your belt can expose them to the sun

 

[Dr Ray]

I believe that the atmospheric temperature is basically note basically not an issue compared to the temperature on firing.
As Rule 303 says, keep the cartridges out of the sun.
If the 40 degree temperature is an issue then perhaps anything over 35 degrees will be too.
Powders these days from what I’ve read are basically temperature tolerant.

 

[Ray B]

Fifty years ago I spent some time in a 155mm howitzer firing battery. I was just the communication link between the observer and the Fire Control Center so I wasn't involved in the calculation to determine how much powder and what direction and angle the 97 pound bullets were fired to arrive on target. However I did know the various variable that were used in the calculation and one was powder temperature. To accomplish this there was a thermometer (industrial size and strength) placed in the powder (which was in flammable bags) in one of the bunkers. The highest temperature I recall being used was 128 F, the low was 75 F. The powder was extruded and about the ratio of length to diameter of 4350, but was about an inch long and 3/8" diameter. What would be informative would be to learn the function graph of the effect of powder temperature on the calculation. At the time computers were rare and at the firing battery they used a function specific slide rule. I wonder where information on these obsolete slide rules could be found on the internet. One may provide some guidance on the effects of ambient temperature on the burnrate of powder.

 

[GuttormG]

Tested this last winter, by fireing the same load from 2 rifles (308win and 7mm RM) over the chrono every time I was at the range (2-3 times a week), temperatures from -10 to +15.
1 degree change of temperature resulted in average in 1m/s change of speed.

 

[Rule 303]

Ray B I think those slide rules were made powder specific for burn rate etc. I know with the ADI powders that are Temp stable have ingredients that non temp powder does not have. IE AR2209 will be chemically different to say N204.

I could be wrong about the slide rules. I would think though that ballistic programs, such as Quick Load, would have the required logarithm built into them.

GuttormG, what powder were you using?

 

[Divernhunter]

I have used the same loading for temps at 115*F and -2*F. Never had a problem. I do not try to hunt at such temp extremes but it has happened.