Powder Temp Sensitivity

[truck driver]

Anyone seeing where Reloader 26 is temperature sensitive?
I did a 15 shot ladder when it was 80 degrees and today it was 56 degrees and my velocities were 60fps slower plus the ES was all over the place.
Granted I was testing seating depth trying to tune the 300wm .308 180gr AB but never expected to see such a difference in velocity. Over nine shots with 3 each .010" seating difference where I went deeper with seating there was a ES of 111fps with the same powder charge.
After trying a fast node and a slower node I don't think my rifle likes RL26 or any other Reloader powder since it was squirrely with RL19 also like a 206fps ES for three shots.
Neither powder charge was max but still with in pressure ranges.

 

[SJB358]

Changing seating depth is just like changing the powder charge. Unless you’re making small changes you’re basically changing the size of the engine and ultimately changing the flat spot.

Small seating changes probably won’t be as noticeable but moving as much as you were with your loads you’re going to have decent speed changes.

I’ve not noticed 26 being bad as far as temp changes myself. It’s been pretty stable from 30-90 for me.

 

[truck driver]

Scotty, strange I never noticed the velocity swing when I was testing the 7mmRem or the 338wm but they don't have the free bore my M70 300wm has. If I hadn't replaced the mag box and bolt stop to accommodate extending the OAL I could have never reached the lands with the standard length box.
OK I just answered my own question and deleted it.
Even though I was decreasing powder volume by seating deeper I was increasing the jump and free bore causing less generated pressure so less velocity. Also I'm still not compressing the powder charge with RL26 when seating the bullet to .080" off the lands. Makes me wonder if I should have seated deeper to get some compression.

 

[NYDAN]

Rodger,

On this webpage:
https://www.rokslide.com/forums/long-ra ... pment.html

I found this quote from an Alliant representative:

About temp sensitivity, here's an email from Alliant when I asked about the powders for my 28 Nosler build.

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

 

[truck driver]

Thanks for the link Dan. I read some of it but the back round colors were giving my eyes a fit.
I'll try reading more in the mourning.
I now know what my problem is and why it happened so I just need to make adjustments to compensate.

 

[Supercat]

Rodger,

On this webpage:
https://www.rokslide.com/forums/long-ra ... pment.html

I found this quote from an Alliant representative:

About temp sensitivity, here's an email from Alliant when I asked about the powders for my 28 Nosler build.

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

So I am finally nailing down a load for my 7mm Rem Mag with RL33 and I am reading the above, from Alliant no less, that RL33 IS temp sensitive UGH! Before I started loading with RL33, I did a google search and I didn't really see much about RL33 being temp sensitive.

How much should I worry about this? Enough to scrap it and start again with another powder?

I am loading in my 70F house, planning on deer hunting in 32F and shooting prairie dogs in the blazing sun at 95F.

Do I need to worry about this? I am fairly new to reloading so I would love to hear your thoughts on this!

Thanks!

 

[SJB358]

I don’t worry about it Supercat. I’m using 33 in my 7mm MSM with 175’s. All powders are temp sensitive but if you’re running up against redline at 32 I’d suspect you’ll be dangerous at 95. I develop most of my stuff in the heat and thus far I haven’t had issues with any of the to normal ranges. I’m not a LR shooter, with 600 yards being my outside limits.

I do believe what some folks see as temp sensitivity is lot changes. Heard it a bunch where a fella will buy a lb in the summer and develop a load and then crack open the new can bought later on then test it in cooler temps and think it’s temp.

Lot changes are a much bigger deal to me than temp sensitivity. If your load is made on a fairly decent node it’ll work. If you’re on a teetering spot it can fall either way.

 

[Supercat]

I don’t worry about it Supercat. I’m using 33 in my 7mm MSM with 175’s. All powders are temp sensitive but if you’re running up against redline at 32 I’d suspect you’ll be dangerous at 95. I develop most of my stuff in the heat and thus far I haven’t had issues with any of the to normal ranges. I’m not a LR shooter, with 600 yards being my outside limits.

I do believe what some folks see as temp sensitivity is lot changes. Heard it a bunch where a fella will buy a lb in the summer and develop a load and then crack open the new can bought later on then test it in cooler temps and think it’s temp.

Lot changes are a much bigger deal to me than temp sensitivity. If your load is made on a fairly decent node it’ll work. If you’re on a teetering spot it can fall either way.

So glad to read that;(

I am also shooting 175's but in a 7MM Rem Mag. I am probably going to end up within .2gr of 78.0gr. I loaded all the way up to 79.0 and just got this bit of a crater so I figured that I would back off a bit even thought the cratering was my only sign.

 

[jimbires]

RL26 in my 7 rem mag is loosing about 0.5 FPS per 1 * F . 48*F - 70*F was a 13 FPS change in velocity . the average guys extreme spread is more than this . if you're hunting inside of 400 - 500 yards temp sensitivity is not that important . if you're trying to set a world record in 1000 yard BR , or hunting way out there , you need to be testing this stuff . only you know what you can adjust for , to make it acceptable to you .

I use RL33 in my 338 lapua , I don't have problems with temp sensitivity getting so wild that I can't dope for it out past 1000 yards . I can't find that info right now , but it's not bad at all .

I use RL22 in my 7 rem mag . I didn't realize it's a crappy powder , until I started to read how bad it is on these forums . it must be the worst powder going . I just don't see any problems with it out to 600 yards . I should have some temp info on it somewhere too .

I've noticed that things seem to get bad ,with about any powder I've used, when the temps get in the 90's on up . most of my loads are right around max charges .

 

[Supercat]

Thanks Jim!

I am not a good enough shot anyway to worry about the ambient temp changing my POI at 1,000 yards but I am worried about the load becoming dangerous in 95F in the sun, which I loaded in my 70F house.

My load that I wind up going with won't be on the verge of over-pressure but it will be in the max range.

Whatdaya think?

 

[SJB358]

I use about the same load as you, at around 83.8 grains in my Mashburn with 175 Woodleighs for 3090 in RWS brass. I have about that much more capacity than you in your Rem Mag, so I’d say you’re in the right ball park with your loads and speeds.

 

[270elk]

My experience with RL 26 is limited variation across 30-80 degree temperatures. I shoot the RL 26 in my 270 and my 300WM. I am a hunter, not a long-range target shooter so some variation is no big deal. I limit my shooting to no more than 400 yards. If my animal is beyond 400 and I can't figure out a way to get closer the animal walks. My recent Wyoming hunt I used a 130 grain bullet with the terrible RL22. I experienced temps in the low 30s and no problems with RL 22 at my self-imposed hunting ranges.
When RL26 came out the word on the blogs was this was a temperature insensitive powder. Up until this post I have only read that praises about the stability and velocity of the powder.

 

[jimbires]

Thanks Jim!

I am worried about the load becoming dangerous in 95F in the sun, which I loaded in my 70F house.

My load that I wind up going with won't be on the verge of over-pressure but it will be in the max range.

Whatdaya think?

I think you might be misunderstanding what temp sensitive means . it does not matter the temp that we are loading in . it is a change in velocity due to changes in the ambient air temp we are shooting in . cooler temps will lower our velocity . warmer temps will raise our velocity . my best advice for going out shooting is to keep your ammo out of direct sun . if you're going to be in an open field all day keep your ammo in maybe an insulated cooler , no ice or anything . and keep the cooler in the shade from the shooting bench . if I'm just shooting for a short amount of time , I'll just throw my hat over my ammo box , or put it under my shooting mat , on the side my body is casting a shadow . direct sun can cause your ammo to be over heated . also try not to let a round lay in a hot chamber and get cooked waiting for the shot .

 

[dougduey]

With RL26, I've personally found (and have read that others have had the same experience) that it can act up when the temp is over 80 degrees. Best to do load development below 80 degrees if you can

 

[RiverRider]

I'd take the opposite approach and do load development when temperatures are 95 to 100 degrees F. That way I could be confident that the load would not act up on me if I was to shoot it at---you guessed it, 95 to 100 degrees. At 70 or 50 or 30 degrees, no sweat. Pun fully intended.