Temperature Sensitivity of Alliant Reloder 26

[Engineering101]

Interesting thread. I'm headed out the door right now going to the range to test the temp response of a RL-26 load in my 260 Rem to the 83 degree weather. The load was developed in 56 degree weather and I know that it shoots really tight at that temp but if you speed it up about 40 fps it will spray. I'm testing to see if I reduced the load enough to avoid this since I do want an "all temp" load. I'll report back to give you another data point.

 

[codyadams]

I do enough hot weather shooting that I need a hot weather load. Two years ago it was 87F on a Wyoming elk hunt at 7,000' in late October, not the norm but it happened so we need to be prepared. I thought the Sig Kilo 2400 AB has some function for powder temp/speed adjustment but I've been too busy to take it out of the box let alone read the instructions. I have Andy's video to watch haven't gotten around to watching it.
As far as barrel temp goes I use a rechargeable air mattress pump with a variable speed control to cool the barrel off as it takes forever when it's this hot. All ammo is at ambient temp and I'm out there for half the day plinking with other rifles while things cool.
I will probably drop this load down to ~92.0 grains so I'm not over max when it's hot then go from there. Or have a hot and cold weather gun. Or i guess I could just have two different load profiles for the Kilo 2400 if they are that different. Perhaps somebody who is in the Kilo know can comment.

Ya, it doesn't usually get that hot here, the hottest I have seen while rifle hunting is about 78° during antelope, most of my rifle hunting is 50 and below, down to single digits. Maybe I will test my load on a really hot day, see if I can go shooting on one of our few 90° days just to see the difference

 

[Engineering101]

Here is my range report from yesterday afternoon when it was 81 degrees at the range. I was shooting a 26" custom barreled 260 Rem loaded with 45.8 gr RL-26 and 143 gr ELD-Xs from 200 yards with a Lab Radar chrono. A load of 46.0 gr shot 0.359" (3 shots) at exactly 2,800 fps when it was 56 degrees the other day. I reduced the load by 0.2 gr to the 45.8 gr I mentioned to get a little margin because it went bonkers at 46.5 grains where average velocity was 2,834 fps. That is what I was testing to see if it would go bonkers again with 0.7 gr less powder but with a 25 degree temp increase. And yes it went bonkers again producing an average velocity that was almost the same as before (2,837 fps) when using more powder in cooler weather.

To summarize:

56 degrees, 46.0 gr = 2,800 fps, 0.359" group
56 degrees, 46.5 gr = 2,834 fps, 1.984" group
81 degrees, 45.8 gr = 2,837 fps, 1.328" group

At velocities between 2,710 fps and 2,800 fps this rifle shoots 0.35 MOA or better but as I mentioned it falls of a cliff between 2,800 fps and 2,835 fps.

Bottom line: I've got to take at least another 0.5 gr of powder out of the case if I want to use this load when it is 81 degrees though it is probably just fine as is at hunting temps. So yes, RL-26 has enough temp sensitivity that you have to so something about it if you want to operate both cold and hot.

 

[Antonio m]

This is useful info.

Thanks

 

[dminn1]

I ran an informal test on Reloader 26 Temp sensitivity after noticing a significant velocity increase on a 85 degree day earlier this month. This test was by no means scientific but I think it shows a useful result. I am shooting .243 Win with Berger 105g Hybrids, Win brass, Tula LR primers. For the test I took 6 rounds loaded to the same charge and put 3 in ice in the cooler for 15 minutes and 3 rounds in the direct sunlight for 15 minutes. Outside temp was 87, humidity 70%. The rounds were removed from the cooler or the sun one at a time and fired in the rifle about as soon as the bolt was closed. Velocity was recorded on a LabRadar.

Ice cold rounds: 3205, 3218, 3203 avg 3208

Sun heated rounds: 3298, 3269, 3275 avg 3280

Ambient temp rounds averaged 3250 fps. When this load was developed it was 70 with low humidity and the load averaged 3200 fps.

That is a 72 degree spread through what is likely to be about as severe of a temp spread as you would ever encounter in the field. My chrono data seems to indicate that this powder is most sensitive when the temps move above 80 degree as that is when I have noticed the only significant velocity spreads. I will have to wait for fall and cooler weather to test this as I developed this load in 65 to 70 degree weather.

 

[Dranger45]

Good to see useful info and statistics on here. We are looking for a tough tonneau cover to keep the guns and stuff dry and secured in the truck bed even on heavy rain. Leaning towards one piece hard top but there should be a good ventilation especially on hot days.

 

[woods]

Good to see useful info and statistics on here. We are looking for a tough tonneau cover to keep the guns and stuff dry and secured in the truck bed even on heavy rain. Leaning towards one piece hard top but there should be a good ventilation especially on hot days.

Don't think it will have much ventilation but yesterday installed a tool box edition Access

Entry/exit level with tonneau closed

http://imgur.com/K2CQj7G

Ride height 2 with tonneau open

http://imgur.com/ca8HMSL

Edit: f'ing photobucket is history if they expect me to pay $400.00. So imgur only lets you link.

 

[Dranger45]

Woods that looks pretty good but yeah, lack of ventilation.

 

[parshal]

I did a test a couple weeks apart using the same lot of reloads. The first day it was 54 and the second day it was 25 degrees. I think this is more indicative of the way we use our loads rather than trying to cool/warm loads for testing. The initial reaction on the Reloder 26 thread was that my results were not the norm. However, reading the tests here it's not so off the mark.

I lost 2 fps per degree with a 29 degree temperature change.

22 Creedmoor
82 grain Berger
45.5 grain R26
CCI 200 primer
Hornady brass

These were fired using a Magnetospeed v3. I fired 15 rounds of the same lot of loaded ammunition a couple weeks apart at the same range and actually the same bench.

 

[maninthemaze]

Here's a quote from Alliant from last year. They did tell me that they didn't recommend R26 for the 28 Nosler because the fill ratio would be too little.


Eric,
Alliant has three temp stable propellants by their chemistry. These are AR-Comp, Reloder-16 and Reloder-23. Reloder-26 by its chemistry is not temp stable, but in most applications it behaves much like a temp stable propellant. The Reloder-33 is not at temp stable propellant. That being said, all of our propellants need to pass, by lot, testing procedures in a wide range of temperatures, wider than any self-respecting human would be hunting or shooting under.
As for load data for the 28 Nosler, Alliant has no tested load data for this cartridge at this time.
I will submit your request to the engineering lab for possible future development. But, there is no timetable as to when this may be looked at for development.
Thanks,
Duane V.
Technical Services Rep
Alliant/Blazer/CCI/Speer

 

[Bowfishn]

I posted this also in the Reloader 26 thread but I thought it may be relevant here as well.
When I shot with it the other day with 147 ELD-M out of my 6.5 Creedmoor Temps were 83 deg far. , it shot the exact same average velocity of the day I shot at 61 deg far. only my 5 shot average had a SD of 1. When I average in the 10 shots from the previous shoot the SD goes to 3.8 fps.
48 gr RL26, 147 ELD-M, Nosler brass 52.7 gr H2O, BR2 primers 2930 fps, 26" X-Caliber barrel. Velocities measured with a MagnetoSpeed Sporter.
The way the weather has been running around here this year I doubt I will have a chance to test any loads in the 90 degree mark.

 

[Hiwayman92]

Great test Cody. I'm going to start shopping for the big jugs or RL-26 because it's fantastic in 3-4 of my guns!

 

[J E Custom]

Thank you Cody, very informative test. I wonder what a test at higher ambient temperature would show. Say 60* to high 90* and how that would impact at 20-40* hunting temperatures. I ask because I shot pressure tests at 75-80 degrees in a 6.5 Sherman with RL-26 vs Retumbo. I got definite pressure @ 3,100 fps with RL-26 and 3,150 fps and no pressure w/Retumbo. Expected exactly the reverse, based on other's experience.

Cody's test Is just what I have found with the RL powders at Lower temperatures. (Anything below 60o is considered a cold front here is Texas). What I have seen is that "all" powders are heat sensitive at high temperatures (90 to 100+) some more than others. As the temperature gets higher the velocity spread also goes up.

With the best extreme powders (Not very heat sensitive) the velocity spread is normally less than 10 to 15 ft/sec at the highest temperatures and some are as much as 150 ft/sec (I have an accuracy load for my 7/08 using H 414 that is 3010 ft/sec during the winter (30o to 50o) and jumps to 3153 in the summer (average temp 95o) and is to hot to shoot at this time of the year).

Most RL powders are in the 30 to 40 ft/sec range in very hot weather but the "New" stable powders like RL 16, RL 23 and RL26 May change that with more testing.

Just what I have found using different powders.

J E CUSTOM

 

[Engineering101]

JE - you lumped RL16/23 with RL 26 but only the first two are temp stable per Alliant who imports them. RL 16 and RL 23 are manufactured by Bofors in Sweden using a process that yields great temp stability. RL 26 along with RL 33, RL 50 and RL 17 are made by Nitrochemie in Switzerland using a different process and they exhibit "moderate" sensitivity to temperature changes (0.5 fps/ degree F per Nitrochemie) but they are very high performance powders. I can live with the temp drift of RL-26 (which in my rifles seems to be more like 1 fps per degree F) given it will outperform everything else in many rifles with an ES approaching single digits but you do have to keep in mind that it will drift enough to knock your pet load off its node if the temp changes as little as 20 degrees or so from when you developed the load.