Home Forums Reloading Big Game Rifles IMR Powder?

Have any of you guys ever experienced temp. sensitivity issues with IMR powders?
Thanks, Sam

Thats the main reason I like the IMR line..only think I have had be silly was some RE15.IMR almost flawless..

Sweet!
I was visiting with a longtime reloader this morning and he really likes IMR4831 for a bunch of his rifles including his .300WSM. I'm gonna give it a whirl...

I think the temp sensitivity is more a new fad/trend than anything. If you hunt in temps below 20*, then develop a load at that temperature. Same applies to higer temps above 70*. I have found insignificant differences with several powders until the temp drops below 30*. IMR has been very consistent for me.

I have to agree with goose20444 to a point. I don`t see much difference in any of the powder brands from say 70*F down to too cold for this boy to hunt. I have however seen a few that seem to have changes at temps of 85*-90*F and up. I tend to believe now the difference in sensitivity is more of a heat problem then cold.

I tend to agree with the fad aspect, also. Powders have always lost a little oomph when it's cold - just like any chemical reaction. But at least that's not hazardous. Having pressures zoom when it's Phoenix in August hot - well, that's something else.

It's quite an accomplishment that the makers have managed to smooth out that performance shift. But it's also not that important to us as hunters. If you find a powder that your rifle loves, use it and don't worry about the temperature issue unless you load to max where it's cool and then take the ammo to a hot place. In THAT instance only, you might want to ease off your powder measure's gas pedal a mite.

I have used Dupont powder since 1953. Back then thats all there was along with Hercules Hi Vel and 2400.

Now its called IMR powder. The IMR rifle line is not very temperature sensitive but on the other hand all powders react to hot summer heat. Just keep that in mind if your load is on the edge now in the winter.

I have had way more problems with ball powders in the heat.

To me the Hodgdon 'extreme' is just marketing but some of their powders are excellent as are the Reloaders.

I was testing the 243 last Monday and it was getting to dusk. The loads were Varget and IMR's 4064 pushing the 70 gr BT. There was a ball of fire from the Varget and no flash from the 4064. The 4064 also shot the best groups.

That's my main concern!
I've been doing alot of shooting lately(10-30 dergrees) with H4350(supposedly temp. insensitive). I'm worried about this summer when I'm out fooling around camping/shooting and it's 90 degrees.
The rifle likes more speed otherwise I'd just use reduced loads...

I'll run a few over the Chrony on a hot day just to be safe...

Thanks for the reply fella's. I'll just cook up a reduced summer brew if they're runnin' too warm.

SamO, I wouldn't worry too much about running your winter loads over the chrono in hot weather. Just be aware of the classic high-pressure signs like harder bolt lift, flattened primers, ejector groove or hole imprints on casehead, shiney marks on casehead, casehead extrusion into extractor cut, casehead expansion greater than 0.001", etc.

I've used IMR-4831 in my .300 Win Mag since 1975 and have never had ANY temperature related problems with my loads. And that includes loads worked up in cold weather and then used in hot weather. And most of my .300 Mag loads are close to max because if I could get by with less, I'd rather use my .30-06 or .308.

But, as others have said, if I was using a load that had proven to be right at max in cold weather, I'd definitely back off a tad in hot weather and work back up to the hot weather max, no matter what type and brand of powder I was using.

Right on, you've been using the IMR longer than I've been alive!
It's very reassuring to hear from folks with alot of experience.
Thanks.

I had to smile when a few of you mentioned things would be fine below 70 degrees. Hell that is the low around here several months of the year.

I have found Hodgon's claim that Varget is not very sensitive. I can attest that a 22-250 had velocities that changed little from 105 to 40 degrees. (yes it sometimes gets that cold here)

Hodgon had small leaflet that came out,it was one of the earliest publications on their extreme powders. In it they compared their competitor's powders. They showed Varget with the pressure/velocity changes as the one with the least changes AND they showed IMR4064 as being very similar. In fact IIRC IMR 4064 beat several of the extreme powders. Anyone remember reading that? I realized that 4064 was pretty special after that. Found it strange for them to let us know other manufacturers had powders that were as good as the extremes.

Sam, Dupont makes no claim to being temp insensitive. Although I have never tested my favorite IMR loads, I DO think IMR4831 is more temp sensitive than H4831. I 've chrono'd lots of H4831 and IMR4831, and I generally see more ES change in temps with IMR4831 than H4831.

And some loads probably exhibit more or less sensitivity than other particular loads.


Casey

Good point.


Casey

I have a very simple answer to the temperature sensitivity issue. Just chronograph your favorate loads at around 75 degrees, then again when it is in the 30 degree temperature range and compare the differences.
The powder techs have told me that it just depends on the load that you are shooting. Different reactions from different loads.
Personally, with my load for a .300 Win. using RL-22, it looses approximately 2 fps. for each drop in degree of temperature from around 70 degrees down. On the other hand, H-1000, an extreme powder, is very consistant from 90 degrees down to 28 degrees for me.
Jim

From -20 to +20 never had any issues with 7828.As for the other IMR powders can't see why there be any difference..

Over the years I have used more IMR powder than all others combined, except maybe Red Dot and Unique. I've shot in temps in the hundred and teens to the minus ones to thirties and never noticed any accuracy, pressure or performance problems.

4320, 4350, 4895, 4831 cover a large range of applications.

My "pet" hunting load for my .300 Savage yielded a chronographed 2680 fps using a 150 grain Nosler Ballistic Tip bullet in 80� to 85� temperatures when I was developing the load.

I had a "situation" come up wherein I also fired the same load in cartridges loaded at the SAME TIME as those that chronographed at 2680 fps. However, this time, I fired those rounds at 35� temperatures and chronographed those rounds as well. They averaged 2630 fps... or a drop in muzzle velocity of 55 fps with a temperature drop of 50� to 55�... or, basically a drop of 1 fps in muzzle velocity for the loss of each degree of temperature.

This was NOT a "scientific" experiment... and it may be that the actual "drop" in muzzle velocity is not consistently 1 fps for each degree of temperature loss.

I'm merely reporting the results of my test... other's results may vary.


Strength & Honor...

Ron T.

Sam:I've been using it since it first appeared as well; IMR 4831 has always been a good powder.To answer the question specifically,yes I have seen it vary with temperature. If I worked up loads in August/September,I noticed a reduction in velocity chronographing those same loads in January/February.

Something I DID notice is that the variation was greater in the 7 Rem Mag than it was in the 270.Could it be a case capacity issue? I do not know.....

I do know I killed a lot of game out west with both cartridges loaded with IMR 4831. I still use it today.

I've not had any temp-sensitive issues with IMR-4064, even while hunting at 100 + degree temperatures in Africa.

By the same token, I'll also agree that H-4831 (even the old WWII surplus stuff that was uncoated) is less temp-sensitive than IMR-4831.

I tested a 338 Win. Mag. handload with 250 gr. Noslers and 68 gr. of IMR-4350 that delivered 2665 fps. on a chilly day in April, and 2698 fps. in July. No signs of excessive pressure on either day, and I don't think that some 30 fps. variation for a temperature change of 40 degrees is necessarily a great big deal to get worried about.

It's not an IMR powder, but I've also used supposedly very sensitive Reloader 22 a great deal in some very hot weather in various parts of the world in the 300 Win. Mag., and I've not had any problems at all with high pressures.

The whole thing is, you simply have to use good judegment and makes sure your loads are safe in hot weather by working them up very carefully and testing them in hot weather, and also in cold weather.

Just two days ago, a Federal cartridge technician told me that they test all of their ammo at temperatures from 50 below zero to 150 degress above zero, and that COLD temperatures had a greater effect in terms of driving up pressures than did hot weather. What powders they're using I have no way of knowing, but apparently those cold temps somehow change the chemical composition of the powder. That's the concept we discussed in brief, but I'm sure there's a good deal more to it than that.....

AD

Allen: Do you think the increased pressures in cold weather could be due to the rifle itself contracting very slightly, due to the cold, making the bore just a wee bit smaller? Sorta like a door jam shrinks and swells from moisture? I really have no idea, but the thought crossed my mind.......

I read an article by that guy McPherson in Precision Shooting that talked about pressures and cold weather;bottom line was everything just resisted ignition in the extreme cold...

I have had no trouble with RL22 in hot weather...nor in cold weather for that matter..