IMR Enduron 4451 Temperature Sensitivity

Some of you asked for a follow-up to my testing of IMR 4451 in my .243 Win. (See the post in Ammunition and Reloading, “Who has tried the new Endurons, specifically 4166?”) My main concern was to find out for myself if IMR 4451 is temperature-insensitive, as claimed. I tested it with Nosler 95 gr Partitions and Hornady 100 gr BTSP’s. I also compared it with IMR 4350, which I have used for many years, and have found to be quite temperature-sensitive. I used loading data from Hodgdon’s website as a reference point for my testing. Tests were conducted at 80 degrees outside air temperature (OAT) and twice later at an average of about 35 degrees OAT. Data at 80 degrees was fairly straightforward; data at 35 degrees was a bit erratic, perhaps because my chronograph was right near the lower limit of its operating temperature range. Here’s what I observed:

1. 95 gr Partition and IMR 4350. Max velocity was obtained with 41.8 gr. Velocity began to decrease slightly with increased charges.

2. 95 gr Partition and IMR 4451. Max velocity was obtained with 41.8 gr. About 10-15 fps faster than with IMR 4350. Velocity began to decrease slightly with increased charges.

3. 100 gr BTSP and IMR 4350. Max velocity was obtained with 41.8 gr. Hodgdon says max velocity is at 42.0 gr, but mine decreased over 41.8 gr.

4. 100 gr BTSP and IMR 4451. Max velocity was obtained at 42.0 gr. About 40 fps faster than with IMR 4350. Hodgdon says max velocity is at 42.7 gr, but mine decreased over 42.0 gr.

5. Velocity drop from 80 to 35 degrees OAT, using the same loads. IMR 4350, 70-80 fps drop. IMR 4451, 50-65 fps drop. Not much difference in temperature sensitivity! Other folks have reported that the Enduron powders are not temperature sensitive, but I don’t see it. Remember, my tests were done with my rifle and my chronograph and my thermometer and my batch of powder. Your results may be different.

That is very interesting. I have been doing load testing with 4166 and the 87 VMAX in my 243. In fact, that is my thread you referenced there. Since it is winter and I am up here in the panhandle, nearly all of my testing has been in colder weather so far (30-60 temp range). As of yet I have no warm temps to compare it to. For me the real test is going to come in the summer when I have to re-tune for 95-100 degree temps. Then I can get some real data and comparisons. I think for the moment I have settled on 39.0 of 4166 as my charge weight on the 87 VMAX, but that quite possibly may have to come down some this summer.

I did pick up some 4451 the other day and plan to do some testing with it using the 100 BTSP Sierra Gameking. Depending on the results I may retest the 87 using 4451 as well since I feel it is a more appropriate burn speed for the mid-weight bullets.

Are you seeing good accuracy using the 4451?

Accuracy with the 100's was very good at 80 degrees. At 35 degrees, I had some flyers. I'm assuming that was me because I was cold and had my arm in a sling, following shoulder surgery.

A couple of questions-

Was both powders the same exact lot as used previously?

What chrono are you using? What was the lighting condition during both cold and hot tests?

Was all the ammo loaded at the exact same time, and one shot in hot and the other in cold? Was one ammo run shot, then were the cases resized then loaded, or all ammo loaded at the same time and then shot at the hot and cold temps?

I have some 7797 I could test if the temp gets down...

Chad,

Powder was same lot, same bottle, both times.

Using a Chrony Alpha Master. I don't recall the lighting on the 80 degree test, but it was probably clear or cloudy bright, same as 35 degree tests. Not high humidity either time.

Same load dates. When I got such a dramatic change in velocities, I loaded another batch to verify the low temperature results. What I called the 35 degree test was actually an average of two tests run at about 32 degrees and about 40 degrees. I have more from the last batch to test again, probably at around 60 degrees.

The velocity drops for IMR 4350 are in line with other, older, tests I have done.

On the chrono, if the sun angle is coming in sideways, like during the winter time, it can effect the reliability of the reading. The Chrony models are known for this.

If the brass was new the first time and reloaded (cleaned, resized) for the second time, you can get a slight change in velocity.

From what I have read, the new Enduron powders are coated with the same stuff H4350, Varget, and others.

Chad, have you ever tested any powders for temperature sensitivity? If so, what were your results?

The 2 powders that I know most about are R22 and H4350. When I first started shooting comps, I ran my TRG in 300 WM with R22. It shot very well with that powder, about 1/3 moa. I ran probably 1800-2000 rounds of 190 SMK with that powder. I did notice when the temps got into the 90's and 100's, that my POI would shift slightly high, and I picked up some speed. I would adjust for this, and stay dialed in. I ran the numbers once, and it was about 1 fps gain/loss per degree. When I ran H4350 in my 260 Rem for several years, I didn't notice the changes from hot and cold like I did with R22. It remained much more consistent. So, I never paid it much attention. I have been loading with IMR 7977 in some of my magnum ammo, and it shoots very well. I like it, but have not shot it enough to know for sure.

I ran some 4451 in my 6mm Creedmore in a recent match and it was good. It took less powder to achieve the same velocity as h4350 does. I plan on testing more and tweaking the load a bit as I was crunched for time.

The most temperature insensitive powder I have tried(tested) has been 4000MR.
Not very scientific but a 50 degree swing in temps and there was not enough difference to mention.
I compared it to N560 and there was a significant drop in velocity when it was cold.
This was in a 280 Rem with 168gr Berger

Yes. The 2000MR and 4000MR powders were designed and developed by a guy named Ken Johnson at St. Marks powder (no longer there), for Alliant. I have spoken to him many times about these powders and have used them on several projects. I personally use 2000MR in my 308 shooting the 175 and 185 Bergers. 2000MR will yield 50 fps faster speeds than Varget will, and it is less temp sensitive than Varget. With my 28" 308 barrel, I get an even larger increase in velocity. It is a great powder. We talked about the newer coatings available on powder to reduce the temp swings. I think 2000MR is a more secret powder that not many shooters know about. 2000MR has a burn speed about Varget, and 4000MR is about a 4831 burn speed. And, it's a spherical powder, which is even more amazing that it's not temp sensitive.

The only one I have had any testing on is 7977 in a 25-06. First day's shoot was in the lower 40's. Speeds where 2980 on average. Second day's shoot was in the upper 70's-low 80's. Speeds were 2985.
Same bottle of powder for both sets. Loaded in virgin hornady brass. 110 gr AB