Temperature sensitive powder

C

Colorado joe

New member
Joined
Mar 28, 2018
Messages
9
Location
Hayden co
Seem to be having an issue at 30° with reloader 17 my group spreads from a half inch at 50° to an inch and a quarter at 30° and I’m wondering if it’s the powder I am shooting 6.5 Creedmore with 140 grain Hornady bthp
 
I cant say for sure as I've not used RL22 any.

I developed a load with temps in the 40's with RL17 and then shot in temps in the 70's and I could barely get the bolt open. When I went to reload those cases the new primers fell right out. WAY WAY to hot of loads once temperatures increased.

I never experienced anything close to that with other powders.
 
The only thing I do different is each night when I clean it I take the muzzle break off and reinstall it I don’t know if that would make a difference or not Group not only grows To inch and a quarter it also moved in inch up or an inch down after everything warms up it goes right back to a half inch group where I zeroed it in 100 yards That’s 15 or 20 rounds later and 10 to 15° in temperature difference
 
I have shot and chronographed RL17 from 0F to 95F and have found it to gain/lose just under 1 fps for every degree F. So from 0-95F you're looking at a velocity spread close to 95 fps.
This was shot out of an '06 with 168 Berger bullets at 3600 ft in elevation.
 
I've had the same issue with other double based powders especially Magpro (hot loads developed in 50 degrees were nearly explosive at 75 in my 300wsm) however I have not noticed it much with Hybrid100V. Some people don't notice anything with temps and others are majorly affected. I've read by powder manufacturers that things shouldn't change much more than a few fps in major temp swings (EDIT: cowboy beat me to this)

Check with a chronograph to see if the velocities are changing. I could also be the temps affecting your shooting style or potential pressure points on the rifle.

I know Alliant is making temp stable stuff so maybe it's worth looking at those.

EDIT: I would also add for you to slow way down on shooting...a warm barrel will change your POI and potentially your groups.
 
Last edited:
Rl powders are all over the place in terms of temperature sensitivity, sometimes they are fine, sometimes its like cowboy says, just depends on the caliber,bullet,charge... That's why pretty much everyone who cares about the subject is shooting hogdon extreme or imr enduron powders.. I have had good success with the enduron in 7-08,30-06,308,300wm, I shoot h1000 in my 7 rm and varget in my 7-08 and those two powders are the most temperature stable I have used. I have a similar experience with RL 22 in the 30-06, developed a load with 62 grains under 165 accubonds, @ 20 degrees it averaged a little over 2900 fps and groups were .3. last week I shot it @55 degrees and my velocity jumped to 2950-60 and the groups opened to 1", small signs of pressure.. I wont shoot that load when its 90 degrees without backing it off .3-5... My advise if your in love with the load and don't want to change powders.. put the bullets in your pocket to warm them up for 5-10 minutes before you shoot and see what it does.
 
Really?
I'm doing my load development when the temps are warm, NOT 20 degrees.
Come hunting season there is no wondering if the load is over pressure or not.
And if i should happen to lose 50fps, oh well. The animal will never know the difference.

And yes i do chrono in hot and cold weather. So i KNOW what my shot is going to do at a certain temp.
 
All powders are temp sensitive. Some are just moreso than others. I only load for hunting rifles. I develop my loads in the temp that I'll be hunting in. I don't shoot in the summer, so I don't care how it does then.
 
RL17 can be temp sensitive. Have you chronographed the load in both temps? Another thing could be that your barrel shoots better when it's fouled. More barrels are ruined by over cleaning than not cleaning.
 
As stated all powders are temperature sensitive but the general rule of thumb is that for every 2 degrees F change you will see about 3.5 fps change at the muzzle which means that your temperature change of 20 degrees would cause about 35 fps difference, this would cause a point of impact shift of around 0.2", not enough change to explain what you are seeing.

On the other hand, it's also a well known fact that the point of impact of a rifle changes with temperature changes due to the reaction of the rifle itself and air density. The general rule here is that the POI will change by 0.5 to 1.0 MOA for every 20 degrees change. Cooler temperatures will cause the POI to shift down and hotter temperatures will cause the POI to climb. So your 20 degree change will cause a POI shift of around 0.5" to 1.0" at 100 yards, just about what you're seeing. It's far more probable that this is what's causing your groups to get larger.
 
rammac said:
As stated all powders are temperature sensitive but the general rule of thumb is that for every 2 degrees F change you will see about 3.5 fps change at the muzzle which means that your temperature change of 20 degrees would cause about 35 fps difference, this would cause a point of impact shift of around 0.2", not enough change to explain what you are seeing.

On the other hand, it's also a well known fact that the point of impact of a rifle changes with temperature changes due to the reaction of the rifle itself and air density. The general rule here is that the POI will change by 0.5 to 1.0 MOA for every 20 degrees change. Cooler temperatures will cause the POI to shift down and hotter temperatures will cause the POI to climb. So your 20 degree change will cause a POI shift of around 0.5" to 1.0" at 100 yards, just about what you're seeing. It's far more probable that this is what's causing your groups to get larger.
Click to expand...

Poi is the obvious effect of velocity changes, air temperature, etc.. but the op describes groups opening up, first thought would be change in barrel harmonics from increased pressure, only way to know would be back off in .1 grain increments and see if the groups close.. or he could have just had a extra cup of coffee that day.. or been shivering... lol..

Here is some interesting research on the subject of powders and temperature
http://precisionrifleblog.com/2016/06/19/powder-temp-stability-hodgdon-extreme-vs-imr-enduron/
 
Last edited:
that makes a lot of sense. out side when I start shooting at 30 the berral is cold I shoot two groups of three and let it cool 20 minute so the barrel don’t Ever get that hot but it does warm up. I have a shooting range in my yard goes up to 500 yards so I shoot pretty much daily
 
You must log in or register to reply here.

Similar threads

B
Case volume physics
Replies
6
Views
545
winmag
winmag
D4570
We are starting load development, 7MMx57 AI.
Replies
12
Views
679
Justabirdwatcher
Justabirdwatcher
R
Help with over pressure but no change to load
2
Replies
22
Views
1K
rideold
R
wtrfwlhunter
Need some load development opinions
2 3
Replies
44
Views
3K
44hunter45
44hunter45
Addicting
7mm08 140BT for elk?
2
Replies
22
Views
2K
buffybr
buffybr

Latest posts

Forum statistics

Threads
111,004
Messages
1,943,303
Members
34,956
Latest member
mfrosty6

Share this page

Back
Top