Temperature Insensitive Powders

[OhHeyThereBen]

This post is not hunting related, just the pondering of a mid-winter North Dakotan. While reading articles about long range target shooting I have come upon the topic of powders and temperature sensitivity/insensitivity. Typically, this isn't something that I would worry about with my hunting rifle as I don't shoot farther than 300 yards. As long as a powder doesn't get over pressured at high temperatures, 50 fps difference isn't going to throw off my shots at all. However, when thinking about the prospect of making reliable hits out to 1000 yards, this may come into play.

The powder that I've been developing loads with for my 6.5 Subaru Crosstrek is Hodgdon H4350, which is one of their extreme powders. They say on their website that the velocities only vary by tiny amounts (I think around 15fps?) between 0-100 degrees.

Has anyone done any testing on this sort of thing? There's really not a lot of information to go off of besides a couple of articles.

 

[1_pointer]

John Barsness as written a bit on this subject. The extreme's get good marks from him as well as some of the new Reloader powders like 23 and 26. IIRC he's also seen differences in sensitivity from the same powder depending on the application/case it's being used in.

 

[VikingsGuy]

I am using extreme powders but have tried to do my development around 60-80 degrees to further minimize temperature surprises. But if things don’t warm up soon I may need to start development with temps in the 30s for my upcoming SA trip. For the more experienced reloaders here, would you be worried if you were handloading near the top end of the published data (but still within it) in late winter/early spring shooting in the 30s/40s then being over presssure on a 90 degree day in the field?

 

[wytex]

We use 4350 for lots of loads and have had no noticeable issues and hunt in every kind of weather. Took my cow bison in very cold conditions with a H4350 handload and have hunted in hot weather as well with no noticeable differences.
That being said I keep my bullets in my pocket except for the ones in the rifle mag. My bison hunt had us trekking for miles in extreme cold before the shot and at 402 yds my bullet hit exactly where I aimed, it had made the trek in the rifle magazine, not my pocket.

 

[jryoung]

I know Pat Sinclair who posts here occasionally has/had run a lot of H4350 in his 260 rem and 6.5 SAUM and shoots in NE MT....that tells me all I really need to know about sensitivity or lack thereof. I think the Hogedon extremes are a good bet as well as the new Reloaders. I see a lot of 6.5 SAUM/PRC guys liking the RL26.

 

[GlockZ]

I can only speak about my personal experience, which is with H4350 and Imr4350. I tested both powders, between loads in my 30-06 & 338WM, and I can that when it comes to extreme temperature differences, the H4350 shines when it comes to giving consistent velocities. From 96 degrees down to 22 degrees, and anything in between, the H4350 averaged, for me at least, a 12 fps difference. As for any other powders out there, I can't speak for them, but there is definitely a difference between IMR4350 & H4350, when it comes to temperature sensitivity.

 

[Pelican]

I’ve tested loads with powders that are supposedly highly temp sensitive, but have not found it to be as big of an issue as some make it out to be. I don’t work up loads in 100+ degrees though or shoot at game over 400 yrds. Here is some of Hodgdon’s data that show that some powder like RE 19 and 22 really don’t loose much velocity between 70 and 0 minutes in some loads.

http://ns.hodgdon.com/smokeless/extreme/page3.php#top

Even with less temp sensitive powders like H4350 or varget, I still test them in the cold to see if there are changes in point of impact, which can happen even if the velocity doesn’t change much.

 

[Rancho Loco]

Temp insensitive powders aren't. They're "less" sensitive.

My findings match many others: Some cartridges are less sensitive than others with the same powder. And sensitivity is not linear with temperature.

Real world testing will ultimately answer the question of how much.

FWIW, I absolutely love H4831SC.

 

[Carl]

Rancho is right, each combination behaves a little uniquely.

That said, if I was picking powders for temp insensitivity, I'd pick the single base Hodgdon line in appropriate burn rates like has been mentioned several times: H4895/Varget/H4350/H4831/H1000/Retumbo.

I did some testing with a Varget load in a 6.5x47 where it showed no velocity change between -12F and ~50F, small primers and all. I haven't noticed variation in my 6 Dashers while running Varget either, but haven't made the opportunity to check it quite as methodically.

 

[.270]

My buddy uses H4350 in his 6.5 creed and gets great groups with it with the berger 140 vlds. Even used the same load for his wife's 6.5 creed and it shoot great out of that rifle as well. He does a lot of long range shooting in the AZ desert and hasn't noticed a different with the temp fluxes from summer to winter.

 

[OhHeyThereBen]

Appreciate the insight here guys. I'll see if I can get some actual testing done once I have a chrono and better setup.

 

[MThuntr]

I know this probably doesn't affect your outcome but I'm shooting Hybrid 100V in my 270 with no noticed change in performance due to temp and it is supposed to be temp sensitive. I tried Magpro in my 7mmRemMag and got dangerously high pressure spikes when temps are around 80 degrees (hot load developed at around 60 degrees) so I stopped shooting that load and will be trying IMR8133. CFE223 is supposedly temp sensitive also but I haven't noticed anything in my 223...my 204 doesn't like it at all but this little rifle never produced consistent groups.

FWIW, I make every effort to use the most "stable" powders I can get like Hodgdon Extreme line and Alliant Reloder's new stable line. I started shooting H100V, MagPro, and CFE223 back when reloading supplies were like gold (post Sandy Hook) and these were all I could get. Once I'm done with these powders they will all be replaced with "temp stable"