Reloder 26, Temperature Stability Sensitivity Data

[Pdvdh]

I'm hoping some members can post any values they've settled on, tested over time, for their observed changes in muzzle velocity per degree F temperature change using RL26 powder.

Convenient would be 0.__ fps change in muzzle velocity, per degree F change in temperature.

I spent a good 45 minutes Google searching this Forum, as well as others. I find little consistency. Alliant claims to expect around 0.5fps/*F. Individuals post everything from -0.2 fps/*F up to more than 1 fps/*F. Yes that's a negative -0.2 fps/*F. The muzzle velocity increased in colder temperatures. Decreased in warmer temperature according to one post.

A year and more has elapsed since many of these Posts/Threads. So anyone have some numbers that have been tried and confirmed over time? Hoping to receive some numbers that don't cover such a broad extreme, perhaps now that more members have additional experience with this powder. I'm just now trying RL26 with a 280 A.I. and a 30 caliber magnum rifle. Thanks.

 

[Bowfishn]

Yes it would be good to see if anyone has more data on the RL26 Temp stability since this thread https://www.longrangehunting.com/threads/temperature-sensitivity-of-alliant-reloder-26.187256/

 

[jimbires]

I'm seeing a velocity loss in colder temps . about 0.5 fps per 1 degree F . I have not checked this in really cold temps . when it was single degree temps , I was sick .

 

[Rhovee]

Same here. I got a tad less than .5fps per degree.

 

[MSLRHunter]

I don't have any experience with RL26, but my experience with RL17 has been that the decrease in velocity with temp decrease has not followed a linear regression. For example, I did my load work at 65*, and when I check velocity at say 45*, I might experience a 0.3 fps/degree drop in velocity. The colder the temp gets, I have seen up to 0.6fps/degree. I hope that makes sense to y'all, it's late.

 

[Barrelnut]

Always liked this chart. Sensitivity is probably between .5 and 1.5 per degree. Problem is sensitivity is not linear. Once you hit -20 degrees, it might be 5 fps!
I do know my test showed .75 fps for RL17. That is what I use for my load in shooter and it seems to work well.
https://www.google.com/search?clien...oECBMQAw&biw=360&bih=616#imgrc=VFOF_4TG23SPHM:

 

[5RWill]

Tag for this as well. Though i wonder how the test are conducted for claims? If some are just shooting in cold temps or if they're actually getting the rounds down to the stated cold ambient temp and then firing.

I picked up some for our 6.5 SAUM, while i'm expecting it to speed up H1000 just isn't giving us the desired results at the moment.

 

[Pdvdh]

I agree the temperature affect on velocity isn't linear. Just hoping that the temps most are testing across and reporting for are typical fall hunting temperatures.
I've tested different temperature rate values with two different cartridges across the same temperature ranges. Here's an example with RL33.

338 Lapua Improved, RL33, 300gr Berger OTM:
Temp Sensitivity between 23 and 68*F = 0.48fps/*F
Temp Sensitivity between -4 and 23*F = 1.44fps/*F
I hunt between 23F and 68F, so it's very workable in that range in my 338 Lapua Improved. Sensitivity picks up once the temp drops below 23F, but doesn't matter to me. I'm not hunting in those cooler temps.

30/375 S.I., RL33, 215gr Berger Hybrid:
Temp Sensitivity between 23 and 68*F = 0.67fps/*F
Temp Sensitivity between -4 and 23*F = 1.44fps/*F
The 1.44fps/*F duplication isn't a typo or error. Just happened to record the same 39fps difference in MV with both cartridges across those temperature ranges. This colder temp data also included MV recorded at 5*F.

Different bullet weights might also change the temp rate change on MV with the same cartridge. I haven't tested for that. I only test the bullet I hunt with.

Anyhow, back to RL26... if members can add the temperature ranges they tested across, that would be a fringe benefit! Two members posting around 0.5fps/*F which is consistent with Alliant's testing. So I'm already off to a good starting value. I'll do my own testing along the way, but it takes time, and I'm just getting started with RL26.

When I test, I bring the ammo and the rifles completely down to outdoor ambient temps. I fire at a slow rate, allowing the barrel to come back down to ambient temp. It's tedious, and it's time consuming. I don't expect most will be doing this. That's fine. Not holding anyone to the nitty gritty details. Whatever you have established will help get us in the ballpark.

Eventually I'll update with my own test results. But, don't hold your breath waiting. I do this over months. Not weeks. I continue to refine it with the bullet I hunt with until I end up with pretty solid numbers for my loads in my rifles. I never collect data in temps above ~72*F. Because it's a cold day in you know what before we ever see a temp above 72*F where I live in Alaska...

 

[brentc]

This is what I found with my 300 WSM. I took 10 rounds to the range to get velocity data from 68.7 grains of RL26 with the 200 ELD-X seated at .020" off. The temp outside was 17*F. For the test, I let five rounds of ammo soak in the cold for 25 minutes while traveling to the range and an additional 30 minutes to let the rifle soak alongside the first five rounds prior to firing them across the Magneto speed. The first 5 rounds soaked nearly an hour and the rifle soaked for 30 minutes at 17*F. The other five rounds were stored indoors at 70*F until they were fired through the rifle.

My 17* F speeds were:
1. 3009
2. 3010
3. 3007
4. 3013
5. 3011
AVG 3010 fps

For the warm rounds, I moved the rifle indoors to soak for 30 minutes at 70*F prior to firing the warm rounds.

The warm speeds were:
1. 3017
2. 3019
3. 3013
4. 3020
5. 3015
AVG 3017 fps

Needless to say, I'm pleased with what I'm seeing with RL26. A 7 fps swing over a 53* temp change producing 3000+ fps with a 200 grain bullet in the WSM case with RL26 exceeded all expectations.

**Update** I've increased the powder charge to 69.3 grains to match the above velocity with a fresh 8lb jug of powder from a different lot. I see no indications of excess pressure and no change in accuracy.

 

[jimbires]

when I do temp testing , I put ALL my gear in the truck the night before , and the truck sets outside . I'm at the range early , before the sun starts to warm up . I'll record the temp , and velocity . then I do the same on a warmer , or colder night .


https://www.longrangehunting.com/threads/reloder-26.172482/page-18#post-1332293

page 18 , reply 241 has my temps .

 

[cjl2010]

I'm interested to see warm weather changes. A lot of our early season coues hunts in Arizona can be as warm as 90°+ and late season hunts as cold as 0-20°.

 

[Pdvdh]

Needless to say, I'm pleased with what I'm seeing with RL26. A 7 fps swing over a 53* temp change producing 3000+ fps with a 200 grain bullet in the WSM case with RL26 exceeded all expectations.

Nice. Yes, that would be a pleasant surprise. That's as stable as stable ever gets.

I can, and expect to, deal with much more temperature-caused MV change than that. However it would be a gift if RL26 happens to also be that stable in my rifles.

Thanks for sharing.

 

[N2TRKYS]

I developed my load in the 80 degree range and got an average of 2960fps. I shot that same load(loaded at the same time as the previous test) when the temps were in the 20s for an average of 3000fps. Accuracy was outstanding for both testings.

This was in a Remington Model Seven SS 7 SAUM with a factory 22" barrel and 160 grain Accubonds.

+++EDIT+++I just went back and looked at my notes. The temp was in the 80s not the 60s. Sorry about that.

 

[Pdvdh]

Because your MV is changing inversely with temperature (which isn't most normal), could you confirm that your load shot 40fps higher MV when the temperature was 60 degrees colder? Slower MV at 80*F and higher MV at 20*F?

Were the rifle and ammo both allowed time to come to the outdoor temperatures prior to recording these MVs?

Last question... Which unit was used to measure these MVs? Light sensing chronograph, MagnetoSpeed, LabRadar...

Thanks