Question on temperature effects

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medalguy

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First some background. I've been reloading for about 45 years but recently moved to a climate where we have a lot of temperature variation summer to winter. Previously I've never had to worry about temperature variation between the seasons. However I now find myself wondering about this. Summers run upwards of 100+ and winters are frequently 20 or lower.

My question revolves around working up a load in winter and the effect summer temperatures will have on the final load. My reloading area is heated to around 65 degrees in winter, so how do I work up a load in winter when I'm shooting tests in 30 degree temperatures so that I can use the same charge in summer at 100 degrees? Is this enough of a variation in temperature to worry about?

I'm wanting to work up loads for .308 using a new lot of BL-C2 powder (actually pulldown WC846) and both 150 gr FMJBT and Sierra 168 gr Match bullets in military brass.

Any input will be appreciated.
 
I have on one occasion stuck the bolt shut on an 03 Springfield due to temperature.

That was when I was young & foolish about 50 years ago.
I had worked up a Very Max load in winter, then found hard extraction and finally a blown primer in 100 degree summer weather.

Now?
I don't load that hot.
In general, accuracy is better, and it kills coyotes & targets just as dead at a grain or two under MAX.

As for temp in your reloading room?
That has nothing to do with it.
It's when your rifle and ammo are near zero at the range in January, and near 100 degrees six months later.

rc
 
I test loads at about 70 since most my shooting occurs between 60 and 80 degrees. When range temps hit above 80 ammo is definitely kept in the shade.

If I hunted in 20 or 30 degree weather I'd test my winter loads under those conditions, but wouldn't use those rounds at temps above 50 or so.
 
Hodgdon show 3.0gr difference between starting and max. loadings for both bullet weights,different type bullets. Add GI Brass that may raise pressure over other brass, i would guess you need to say away from maximum with your BL-C2 powder (actually pulldown WC846). Hot barrel or hot weather, about the same if the ammo is left in the chamber or sun.
 
Yeah I agree 243winxb. I want to develop a middle range load. No sense abusing this old shoulder any more than necessary. What I'm wondering is whether I should wait until spring to start developing a load or if I can work up a midrange load now, and if I will have any problems in summer? Any adjustments I should allow for? It's usually in the 30-40 degree range when I shoot in the winter, but summers can get 100 easy. Any problems??
 
I don't have an answer for you. Using IMR powders have never been a problem for me, hot or cold. The only thing i do not like to do is let a round sit in the chamber of a hot barrel to long before firing.
 
If you stay away from max - use a mid range - then your ammo will be good for all weather.

For example - my 38 spl loads. For a 158 gr LSWC the range for Titegroup is 3.2 - 3.8.
I load mine to 3.5 & they work well in all weather. I've shot from 85 degrees down to about 10.

Yes, I "might" get a frog's hair more accuracy if I worked them up for each season, but that's way more fiddlin' around than I want to do.
 
Thanks guys. I guess I'm worrying more than I need to about the temperature changes. I have lived in a warm/hot climate so long with virtually no major temperature changes that I've never worried about the effects of temperature. I know that if you work up a load in say winter and then shoot that same load in summer, pressures will be generally higher. However I don't usually load to the max and this is really plinking ammo so maximum accuracy is really not the issue, hence the below max limitation.

I guess I'll go ahead and work up a reasonable load below max and go with that. I appreciate the input.
 
Just an FYI, I have had temp problems with WC846. In cold weather, some rounds would produce a huge blast and fireball. It is the only powder I have had problems with in many years of reloading. It was at its worst when using it for my .243. I finally just pulled down the rounds I have reloaded with it. I still have about 7 lbs of it that I will probably use for rotting out some tree stumps. Hope yours is a better lot than what I have.
 
Varget is good no question. Well I have about 65 pounds of WC846 I want to load into 308 so Varget is not an option here. :p
 
I find a 0.2-0.3 grain difference between Winter and summer loads in my 6 BR. Then again I only average about 0.3 in groups at 100 meters.
 
Per Quickload

Example:

.308 Winchester
41.5 grains IMR 4895 w/ Sierra 168 w/ 21" barrel
Zero degrees farenheit -- pressure: 39361 PSI -- velocity: 2388 FPS
Fifty degrees farenheit -- pressure: 43198 PSI -- velocity: 2461 FPS
Ninety-five degrees farenheit -- pressure: 46834 PSI -- velocity: 2523 FPS

So, about 5% change in velocity, and about 8% change in pressure when going from zero degres to ninety-five degrees.
 
Last edited:
VARGET example:

.308 Winchester
40.0 grains VARGET w/ Sierra 168 w/ 21" barrel
Zero degrees farenheit -- pressure: 42983 PSI -- velocity: 2359 FPS
Fifty degrees farenheit -- pressure: 46804 PSI -- velocity: 2426 FPS
Ninety-five degrees farenheit -- pressure: 50518 PSI -- velocity: 2483 FPS

So, about 8% change in velocity, and about 9% change in pressure when going from zero degres to ninety-five degrees.
 
Interesting. I always thought Varget would have less variance although I have never tried it in cold temps. Well I don't plan to load anywhere near max so I should be good with what I'm doing now.

Thanks for all the comments. It's great to have a place where so many are willing to share their knowledge.
 
It's interesting that the big powder companies have not published any specific results relating to temperature effects. A couple months ago I got curious about this same topic. In my case I had a fairly mild .45 Colt load that had worked wonderfully when it was 85 degrees, but when I was shooting it at 25 degrees, it was very sooty, indicating the pressure was much lower.

I was surprised at how little had been published about this. There was some work done a long long long time ago by Hatcher on rifle cartridges. But only a couple published documents by independent people in the modern era. Indeed, the results such as they were were kind of eye opening to me. One of the modern era studies actually did compare H4350, which is supposed to be one of the "Extreme" powders that are less affected by temperature, to the IMR4350, which is old-school supposedly. Basically the results were the same for both powders. So perhaps the claims being made that Varget or any other powder is resistant to temperatures are just marketing hype.

I have often heard though that ball powders are more sensitive to temps than extruded powders. That is just based on observations made by benchrest shooters, but there is probably a lot of truth to those observations. Too bad because I'm really starting to like this W-780 ball powder.

Like I said, it's surprising there isn't more extensive research published on this by the big companies. Perhaps they have done the research but don't want to scare us.
 
Don't forget PRIMERS in the equation as to poor ammo performance in cold weather.

Logical that a weak primer ignition will contribute to inconsistent powder ignition.

There are ample accounts of .22 rimfire ammo having a much greater frequency of misfires when temps drop below freezing.

The Quickload numbers all assume a standard ignition force.

I doubt that anybody could make a convincing argument that 1% Quickload difference between IMR4895 and VARGET is significant.

Use the tables and programs as a guideline.
Before you can be sure of ANYTHING, you need to test specific equipment and specific conditions.

Only thing for sure is hot ammo gets hotter when its hot, and weak ammo is weaker when its cold.
Probably didn't need a slide-rule to figure that one.
 
W.E.G. said:
Only thing for sure is hot ammo gets hotter when its hot, and weak ammo is weaker when its cold.
Probably didn't need a slide-rule to figure that one.
Click to expand...
Well, that's usually the case but not always. The reverse can also happen.

https://www.hodgdon.com/smokeless/extreme/page3.php#top

Please note the AA4350 findings in .30-06.
70* weather the measured pressure was 47,100 CUP.
125* weather the measured pressure dropped to 45,100 CUP.
0* weather the measured pressure rose to 51,900 CUP.
 
Old December 22, 2010, 12:52 PM #19
W.E.G.

VARGET example:

.308 Winchester
40.0 grains VARGET w/ Sierra 168 w/ 21" barrel
Zero degrees farenheit -- pressure: 42983 PSI -- velocity: 2359 FPS
Fifty degrees farenheit -- pressure: 46804 PSI -- velocity: 2426 FPS
Ninety-five degrees farenheit -- pressure: 50518 PSI -- velocity: 2483 FPS

So, about 8% change in velocity, and about 9% change in pressure when going from zero degres to ninety-five degrees.
Click to expand...

W.E.G.,
1) You calculate with Quickload 124 fps change 0 to 90 F 168 gr
2) I calculate with V.3.4 Quickload 115 fps change 0 to 90 F 168 gr
3) Hodgdon's page claims 5 fps change 0 to 90 F 168 gr
4) Kombayotch measures 14 fps change 0 to 90 F 190 gr

http://www.canadiangunnutz.com/forum/showthread.php?p=5026419#post5026419

308_temp.jpg

This Kombayotch Canadian poster included KG-12, in his Copper Solvent replication of testing, and he seems to know how to do a controlled test.

What does it all mean?
I think that Varget is more temperature stable than the Quickload prediction.
 
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