Temperature Sensitivity Test: IMR 8133 and Reloder 26

Just ran a fairly rigorous temperature sensitivity test on IMR 8133 and Reloder 26 in my 7mm RM.

Equipment.

26" X-Caliber prefit, 1:8 twist, fluted heavy sporter.
Sartorius high precision scale for powder charges ( ≤ 0.03 gr ES for charge weights)
LabRadar
Indoor/Outdoor thermometer set (crappy, but within a couple degrees of 2 other crappy thermometers)
175 ELD-X, RL26 and IMR8133, Fed 215M primers, R-P brass, 3.335 OAL (~0.020 off lands).

Method.

1) All rounds were loaded in one session, using my standard methods. Neck turned, ~4X fired, annealed every firing, FL sized (shoulder bump 0.002"), sinclair neck mandrel expanded, and trimmed. Pin tumbled, graphite lube in neck.

2) An aliquot of 5 rounds was placed in a cooler with ice (~32° F) for transport, and a second aliquot was placed in another cooler with 3 Nalgene bottles full of boiling water. Since it was a steady 29º F for the shooting session, the "Cold" aliquot was taken out of the cooler, and left outside on the ground next to my shooting position, with a thermometer in the lid of the ammo box. Both aliquots had ample time to come to a near equilibrium temperature (>2 hours), though the "Hot" rounds obviously slowly cooled during transport and setup from ~135° F initial temp, to ~100° F when fired.

3) Rounds were fired in 4 shot strings, 2 "Cold", then 2 "Hot" (to ensure maximum chamber heat for the "Hot" aliquot). The barrel was then allowed to cool to ambient temp before the next 2x"Cold" and 2x"Hot" string of 4. The last two rounds were fired 1x"Cold" and 1x"Hot", for a total of 5 shots of each temperature.

4) Both sets of loads were on the toasty side for this rifle (I was exploring top end loads for these powders), and based on the velocities, are probably at or slightly above SAAMI max.

Results.

Reloder 26 - "Cold" average = 3010 fps, "Hot" average = 3015 fps. ~0.1 fps/deg
View attachment 237216

IMR 8133 - "Cold" average = 3060 fps, "Hot" average = 2989 fps, -1 fps/deg (dubya tee eff!?!?!)
View attachment 237217

Discussion.

Reloder 26 performed admirably, with an ES of 21 fps and SD of 8 fps across all shots.

IMR 8133...I don't know W.T.F. is going on here, and can think of no explanation. ES/SD was rather high for each aliquot, but well outside error. I've replayed the shooting in my head over and over, and I'm 99.9% certain there's no way I reversed the shot order, as I intentionally shot the "easy to grab" cold rounds out of the box at my elbow first, then shot the ones I had to dig out from under a wool shirt and inside the cooler, 2nd. I know for a fact that the last two were 1x"Cold" then 1x"Hot", as I pulled some hot water out to give to my dogs since the experiment was finished, and those two also showed the extreme difference (Cold 3078 fps, Hot 3000 fps). As also mentioned, I loaded these in the same sitting, and they were only separated into aliquots this morning when I put them in their respective coolers.

The results for IMR8133 are so odd, that I think it requires a retest before putting much stock in the outcome. I will hopefully get a chance in a week or two when the grubby weather that's inbound has passed. I'll probably use my 264WM for that, to get another data point.
Well dang it that just complicates things further! Also thanks for the scientific approach to this test. They say the more you know the more you see how much you don't know and this is relevant here. I'm loving 8133 in my 300 win mag with 225 elds. But I did discover it's not as temp insensitive as advertised. Worked up my load two October's ago. Went to play with it more last July in the heat and about one in three cartridges had a stiff bolt lift and a shiny case head. Nothing extreme or alarming but still...and this business of going slower in warmer temps just makes no sense..:I believe your results, just don't understand them. More pressure and lower velocity....hmmm....
 
Ran an 8133 stability test last winter / spring, from 3F to 57F, on 4 different days. Gun/ammo at ambient when shot. Used a 28 Nosler (26" barrel) and 180 Hybrids sitting on 80.9gr of 8133. Average sensitivity was 0.55 fps/degree. SDs were 9.2 - 12.8, with ESs of 13-30, which has been typical of 8133 for my testing. Barrel was allowed to cool 10 minutes between shots. The stability with 8133 is there....

1609612404569.png
 
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Have not been able to chrono the speed of 8133 in cold weather yet but recently did load development on a 7mag and had a ES of 4, 9 & 12 for 3 shot groups shooting out the B node at 85*

We have shot a ton of 26 and have experienced the 85* pressure spike 26 is notorious for.

So this far our results in the 7RM with 8133 have been excellent...
 
Ran an 8133 stability test last winter / spring, from 3F to 57F, on 4 different days. Gun/ammo at ambient when shot. Used a 28 Nosler (26" barrel) and 180 Hybrids sitting on 80.9gr of 8133. Average sensitivity was 0.55 fps/degree. SDs were 9.2 - 12.8, with ESs of 13-30, which has been typical of 8133 for my testing. Barrel was allowed to cool 10 minutes between shots. The stability with 8133 is there....

View attachment 238208
Your results seem more normal. Higher temp = higher velocity. My temps were going from about -5 to -10 celcius up to 25-30 or so (I believe that's single digits Fahrenheit to about 80 or so). Definitely temp stable but not the king of that particular hill
 
Finally got a chance to retest IMR8133, using the exact same protocol. The inverse T/V relationship is real, and repeatable...:oops:

This time I used 70.5 grains instead of 70.8 (175 ELDX, 7mm RM, 26"), and the velocities were right in line with that change, but the cold rounds still shot WAY faster than the hot ones. I have no explanation...

IMR 8133 - "Cold" average = 3032 fps, "Hot" average = 2974 fps, -0.9 fps/deg (dubya tee eff!?!?! x 2)
Screen Shot 2021-01-09 at 5.53.35 PM.png


I also tested H1000 today (66.3 gr, 175 ELDX), which showed a bit more insensitivity than I expected, but at least it was in the right direction...

H1000 - "Cold" average = 2911 fps, "Hot" average = 2954 fps, 0.7 fps/deg.
Screen Shot 2021-01-09 at 6.21.49 PM.png
 
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Finally got a chance to retest IMR8133, using the exact same protocol. The inverse T/V relationship is real, and repeatable...:oops:

This time I used 70.5 grains instead of 70.8 (175 ELDX, 7mm RM, 26"), and the velocities were right in line with that change, but the cold rounds still shot WAY faster than the hot ones. I have no explanation...

IMR 8133 - "Cold" average = 3032 fps, "Hot" average = 2974 fps, -0.9 fps/deg (dubya tee eff!?!?! x 2)
View attachment 240308

I also tested H1000 today (66.3 gr, 175 ELDX), which showed a bit more insensitivity than I expected, but at least it was in the right direction...

H1000 - "Cold" average = 2911 fps, "Hot" average = 2954 fps, 0.7 fps/deg.
View attachment 240313
That inverse is so strange. I do 100% believe it though. So she's building more pressure cold. I'm going to be laying in bed tonight thinking about this. I wonder if it's just that the chemical makeup of the powder causes it to burn hotter when cold or if there's something else that contributes to the extra velocity when it's cold.
 
I am surprised at your H1000 findings. It is known across many disciplines as being one of the most temp stable powders available
 
I was told by Alliant tech person that RE23 (in 280AI) will be faster when colder. Have not had a chance to explore that possibility. Generally extremely pleased with load work up. Very predictable.
 
Since the case is cold and the gun is cold is it possible the brass case being cold is not expanding as fast or the powder taking longer to burn, burning further down the barrel while still causing a slower but increased pressure curve or pressure spike. Kind of like going from H1000 to Retumbo with the slower burn of retumbo.
 
Since the case is cold and the gun is cold is it possible the brass case being cold is not expanding as fast or the powder taking longer to burn, burning further down the barrel while still causing a slower but increased pressure curve or pressure spike. Kind of like going from H1000 to Retumbo with the slower burn of retumbo.
Don't know enough about the physics, but I can't see how that would affect IMR8133 (cold = faster), in the opposite manner of RL26 and H1000 (cold = slower). The same equipment, materials, and protocols were used for all experiments.

I am surprised at your H1000 findings. It is known across many disciplines as being one of the most temp stable powders available

It's only 4 shots, and both strings have mediocre SD/ES. Almost certainly coincidentally, the "hot" string has a fast "flier" and the "cold" string has a slow "flier". I wouldn't ever remove a flier from data, but it's plausible my results are skewed a bit to the "worst case" due to my poor sample size, and conservative interpretation of data.

Not saying my results are bogus, but I'm a firm believer that sample sizes should be appropriate to the conclusions I draw. I think it might be one of the reasons I've never owned one of those "Half MOA all day long, as long as I do my part!" rifles I hear so much about...;)
 
Retumbo in my 338 NM is very inversely temperature sensitive. My hunting temp is always less than my normal testing temps. I don't like stuck bolts while hunting. I too bought a pound of 8133 to test as I didn't like the inversion. I've noticed it wasn't as temperature stable as I was hoping for. Haven't tested it in hot weather but the velocities and accuracy seems to be there.
 
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