Temperature sensitivity in rifle powders.

[Animal]

Hello folks,

I'm currently working on 7.62x39 handloads with jacketed bullets 123-150. I may explore casting for this rifle, but I'm trying to keep it simple with jacketed bullets at the moment.

The powders I have to work with are Reloder7, H335, H4198 and IMR4227. The first three are the most interesting. I've had some good luck with H4198, but I'm also hearing that H335 seems to provide the best accuracy and want to see for myself.

I am curious about how well these powders function between a temp range of 15-110degrees. The maximum range I'm looking to shoot is 100yds. When I hear about folks disusing temp sensitivity with rifle loads, I'm wondering if there is a good guideline to follow with regard to group size variation at 100yds. My experience handloading for rifle is very limited, so I'm looking for a fairly good baseline of what to expect in temperature swings when shooting to a maximum of 100yds--Georgia temps, specifically. Thanks folks

PS. I understand max loads can become dangerous if the temp is extreme enough, therefore I will be selecting a powder that I can shoot nicely while staying well under the max load.

[pworley1]

I have not used Reloader 7 or H335, but I have not noticed any temperature problems with the others here. Temperature range 0-105.

[groovy mike]

The only powder you list that I have used in 7.62x39 is R& with Hornady .310 123 grain FMJ projectiles.

I don't normally load with R7 but my notes from several years ago said that 20.5 grains of R7 was an accurate load at about 2000 fps and 26-27 grains was "ok, not great" for accuracy. I had not retained any of the test targets and those were the only notes for R7 in my load book.

So I loaded five each of 20.5, 21, 22.5, 23, 24, 25, 26 and 27 grain loads in 7.62x39 with the Hornady FMJs. The cases were fairly full even with 20.5 grains and the 27 grain load was surely compressing some powder while I was seating the bullet.

I took an iron sighted Norinco SKS to the range and tacked up paper plates at 100 yards. It was about 20 degrees F and I was shooting off a rest on a bench. The front sight just about covered the paper plate at 100 yards, so I was not expecting cloverleaf patterns.

The first load that I shot was the 20.5 grain load. It missed the paper plate at 100 yards. I thought that was odd but found later that all shots had been low. The 21 grain load put 2 shots half an inch apart at 6 o clock and the rest off paper below the plate. 22.5 grains put all shots in a playing card sized group on the lower half of the plate (not bad for iron sites and my shooting!). This was the best group I had. The 23 grain test group was abot six inches wide but all over the plate. Oddly the 24 grain group was a beautiful vertical string 5 shots an inch or so apart straight up and down the 8 inch plate (I'm not sure why). The 25 grain load had 4 shots on the outer edges of the plate. 26 grains had 3 shots on paper. 27 grains had only 2 shots on paper. Maybe I was getting cold and tired by the time I got to the last groups, but the results seemed to agree with my previous notes.

Someday I might try tweaking the load development more but I was happy enough that I loaded up the rest of my brass with the 22.5 grain load.

I also have acceptable loads with BLC2 and IMR3031

[357Mag]

Animal -

Howdy !

FWIW -
IMR8208 has proven in testing to be both temp insensitive, and capable of providing low SD & ES numbers; when shot in
things like 6PPC. It's in the benchrest powder burn rate zone, fer sher.


With regards,
357Mag

[Animal]

GroovyMike, Thanks for sharing your experience with RL7. I've got twice as much load data for that powder than I do the others. I wonder if that is a testament to how well it performs.
357Mag, I'll keep that powder in mind. I've also heard that Accurate 1680 is the 'bees knees' in this cartridge. It will be a while before I put another powder on my shelf though. At least until I've gotten results for the 4 I listed.

As far as temperature sensitivity, I'm starting to lean toward the idea that at 100yds, a cold barrel is probably the biggest factor in accuracy. Powder sensitivity is probably a fairly distant second.

[GrocMax]

I bet Accurate 2200 would work well in the 7.62x39.

[lotech]

While you may find a Hodgdon Extreme powder less temperature sensitive than others, try what you already have on hand. With your 100 yard parameter, temperature sensitivity may prove to be an insignificant factor.