My Powder Temperature Sensitivity Test

ltrmc02

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Nov 23, 2011
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54
I know there’s probably lots of information out there on the sensitivity of different powders and there is on many of the Hodgdon Extreme line of powders but I was really interested in IMR 8208 XBR as it really shot well for me in my .22-250 with great velocities but I couldn’t find any good data on it, just many saying that it’s pretty temperature insensitive. Well to relieve my curiosity a bit I did a little experiment to see how different rifle powders compared in the .308 Winchester cartridge and thought I’d post my findings for anyone interested.

Criticize if you want, I would have liked to have done a larger round count of each powder and with a wider temperature difference but due to limited supplies and available time I just shot 2 “Hot” rounds and 2 “Cold” rounds of each powder for comparison. With the exception of the IMR 8208 all rounds were loaded in Win brass with 155gr Barnes Match Burner, WLRM primers and at 2.800” OAL and I decided on the powder charge weight of each powder by going half way between starting and max loads listed on Hodgdon’s website for a 155gr projectile, not necessarily the same one I was firing. As for the Alliant Reloader 15 I found the info on some forum for the min and max load and I knew 42.7gr was safe, for my rifle, as I had been loading a heavier dose behind a 175gr SMK. The RL-15 probably could have used a heavier dose of powder which may have affected it’s difference between the hot and cold firing. I already had some loads made up with IMR 8208 and didn’t have any powder left for this experiment but really the main comparison is being made between the round fired hot vs. cold. My IMR 8208 rounds were loaded in Lake City LR brass at 2.800” with 155gr Hornady Amax and WLRM primers @ a 43.6gr charge weight. I used magnum primers only because that’s what I had. I’m not sure what affects a non-magnum primer would exhibit but this was my test and here are my results. The IMR 4895 had an opposite affect of what I would have thought. I got a sticky bolt and pretty good pressure signs with the cold rounds but not the hot. The temp was 86°F outside with varying sun which I tried to keep the “Hot” rounds in the sun. The cold rounds were inside a small dorm fridge freezer area until fired, I didn’t take the temp reading in the freezer but there was ice build up inside and my frozen dinners were still solidly frozen so below 32°F for sure. I fired a few non test rounds before beginning the test just to not start out testing on a cold chamber and bore. I then started with firing one “Hot” round then running to the freezer, only 30’ away, grabbing the two “Cold” rounds firing them as quickly as possible then firing the other “Hot” round, all of the same powder. I then proceeded through the same steps with the following powders until complete. All rounds were single loaded into the chamber of a 20” Remington 700 XCR Tactical Compact, factory barrel and chamber. *Note, none of these stated loads are recommendations for you to replicate, please consult a reputable reloading manual for safe loading data.*

Varget @ 45.5gr Hot Vel. 2685,2711 Cold Vel. 2710,2715 Avg. Difference (15fps)

Win 748 @ 46.5gr Hot Vel. 2817,2796 Cold Vel. 2699,2711 Avg. Difference (102fps)

IMR 4895 @ 45.5gr Hot Vel. 2769,2757 Cold Vel. 2798,2793 Avg. Difference (33fps)

H4895 @ 44.5gr Hot Vel. 2794,2803 Cold Vel. 2801,2805 Avg. Difference (4fps)

IMR 3031 @ 41.7gr Hot Vel. 2722,2715 Cold Vel. 2636,2639 Avg. Difference (81fps)

Reloader15 @ 42.7gr Hot Vel. 2534,2512 Cold Vel. 2426,2389 Avg. Difference (115fps)

IMR 8208 @ 43.6gr Hot Vel. 2804,2782 Cold Vel. 2753,2773 Avg. Difference (30fps)
 

Daveinjax

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May 21, 2012
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Jax Fl.
Thanks for the information. I'm wondering if anyone has done a similar test but froze the rifle along with the ammo ? It would more closely duplicate real world conditions. I don't live where I can shoot out my back door or I'd do it myself.
 

FEENIX

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Great Falls, MT
Thanks for the information. I'm wondering if anyone has done a similar test but froze the rifle along with the ammo ? It would more closely duplicate real world conditions. I don't live where I can shoot out my back door or I'd do it myself.

+1! Somebody might take up that challenge (I hope) and share with to us. :)

Not a criticism, just a note FWIW ... the average household freezer probably is not set at -32°F.

The temperature range in a Sub-Zero with an electronic control panel is 34° - 45°F degrees in the refrigerator and -5° to 5°F degrees in the freezer.
In units with an electronic control panel, 38°F is ideal in a refrigerator and 00°F in a freezer. Proper Storage Temperatures for USDA Commodities - Food Distribution (CA Dept of Education)

Anyways, GG did similar test and noted that above 80°F degrees is the magic temp ...

Absolutely! There have been many tests on this subject. Many have been published and some data is contradictive but I'll give you my own personal results.

As far as brands go, here's my list from most temperamental to least:

1. Ramshot (because they are all rifle ball powders)
2. Winchester (because they are all rifle ball powders)
3. Accurate (because they are mostly rifle ball powders)
4. Alliant
5. IMR
6. VV
7. Hodgdon


As for individual powders, my list is this: (I'm not going to name each powder here, just a few of the best and worst and a few of the ones in the middle)

most temperamental to least:

H380
H414
WW748
AA2460
WW760
H335
RL25
RL22
IMR4198
AA4350
VV550
H4895
IMR4350
IMR4831
IMR7828
N165
H1000
H322
H4831ssc
N170
N133
Benchmark
Varget


Even though some of the powders listed towards the bottom of the list are great for weather insensitivity, they still exhibit a need to tweek with the charge slightly in temperature changes to maintain a certain pressure. Despite some claims by some manufacturers that their powders will shoot the same from 20 below to 120 above, no powder is perfect. Temperature changes all combustables combustion. Period. It is unavoidable no matter what "coating" you use on the powder. And all powders show markedly different characteristics once the temp gets to and above 80 degrees. Loads worked up above 80 will still work accurately as long as the temp stays above 80 degrees. But loads worked up below 80 degrees F do better shot up to around 75 degrees. Or in other words, loads worked up in cool weather hold their node for a longer temp range than loads worked up at or above 80 degrees F.

I'm not sure why 80 degrees is the unlucky number, but I have seen this be the fulcrum of load development time and time again with every brand and make of powder--especially ball powders.

Also, ...

 
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Greyfox

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My results are quite similar between the Hodgdon, Alliant, and IMR powders. My testing from 20F to 85F has clearly favored the Hodgdon powders as to temperature stability with my various rifles/loads. My preferred powders where temperature variation is a factor are Retumbo, H1000, H4831sc, and Varget. They cover a fairly wide range of my loads and calibers.
 

ltrmc02

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Nov 23, 2011
Messages
54
Not a criticism, just a note FWIW ... the average household freezer probably is not set at -32°F.
I didn't state my freezer was at -32F, I said it was at least below 32F the freezing mark or 0 Celsius. There are some freezers where I work that are set at -30C which is around -22F and that is one cold place to have to go in and work. That kind of cold will freeze your eye lashes and start making it hard to blink in a very short time lol.
 

Dosh

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Arizona
Thanks for the all informative posts. I've found essentially the same results with a few of the powders listed and stick with the Hodgdon Extremes. But, I am sure there are some that will dispute these findings to the bitter end.
 

FEENIX

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Great Falls, MT
I didn't state my freezer was at -32F, I said it was at least below 32F the freezing mark or 0 Celsius. There are some freezers where I work that are set at -30C which is around -22F and that is one cold place to have to go in and work. That kind of cold will freeze your eye lashes and start making it hard to blink in a very short time lol.

My sincere apology; I misconstrued your post below 32F to mean as -32F... my bad.
 

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