Temperature Sensitivity of 11 Powders for .308 Winchester

[BillC79]

The following are data and figure panels from a study I am completing on temperature sensitivity of 11 powders to load .308 Winchester cartridges with 168 grain BTHP bullets. The data may be useful to others.

Powder shortages and previous tests for optimal match bullet powders have left me with 11 different powder types which can be used to load .308 Win cartridges. I want to shoot up some of these powders with two .308 rifles that I use for practice. So I developed data about the temperature sensitivity of each powder in Florida temperatures (34F to 97F) and an adjusted burning factor rate (Ba) to use with Quickload V3.9 for deciding on powder loads for .308 practice rounds.

Methods and other information on the tests are on a website HERE.

Comments/Improvement suggestions are welcome.













Thanks for looking.

 

[Ned Ludd]

Thank you for your efforts in generating this data and sharing it with the rest of us. It is highly appreciated!

 

[rijndael]

I'm glad the humidity numbers were at least mentioned, since it can be a big velocity variable.

F. Firing and Chronometer Procedure
Tests were run in July, 2022 in Gainesville (elevation 176 feet above sea level). Ambient conditions during tests ranged from 75 to 91F and 71 to 87% humidity.

 

[memilanuk]

I was looking back at some of his earlier articles. It's interesting to see the relative 'temperature sensitivity' of some powders (N140 in particular) move around with lot #. It's something I've wondered about but never really tracked.

Personally I disagree with the assumption that N140 can't push a 200 fast enough for FTR @ 1k. I know for a fact that it can, and does all across the country every weekend.

That's part of why I mostly quit using QL... it's burn rate data for N140 and N150 were so far off it wasn't really worth using.

 

[CharlieNC]

Nice job! A lot of work and cost for sure.

 

[Acyr]

Excellent information. Thank you for sharing your results.

 

[K22]

It appears you put a lot of effort into this data - good job.

I've hunted in temperature extremes, varmints in the spring / summer to predators / deer / bear in the fall / winter months. I found that the 'extruded' powders I've used react to temperature changes relatively the same. Where I've noticed a significant difference is with ball powders to the point that I experienced pressure surges in the heat of the summer, loads which were otherwise very stable in cooler months. For this reason, I do not use ball powders anymore. H380 was especially troublesome in the 22 250.

Relative to POI changes due to temperature variations, I wonder how much is due to air density changes versus the powder's reaction to the temperature change? For sure I experience POI change from winter / fall to spring / summer. Maybe it's a combination of both effects.

 

[Straightshooter1]

Relative to POI changes due to temperature variations, I wonder how much is due to air density changes versus the powder's reaction to the temperature change? For sure I experience POI change from winter / fall to spring / summer. Maybe it's a combination of both effects.

Without question, air density will change POI as it effects velocity as the projectile moves down range. But, air density will not change the MV to any measurable effective degree since the projectile is only dealing with the small amount air inside the barrel to that point.

 

[K22]

Without question, air density will change POI as it effects velocity as the projectile moves down range. But, air density will not change the MV to any measurable effective degree since the projectile is only dealing with the small amount air inside the barrel to that point.

Yes, that makes totally sense. Thanks for point that out.

 

[RegionRat]

Many thanks for sharing the work Bill.

 

[Metal God]

Thanks for the info , seems to confirm what's been said for years . Varget is no better unless you push it hard . Had no idea N-140 & 50 were so stable . Going to look into getting some 150 thanks .

 

[RegionRat]

Thanks for the info , seems to confirm what's been said for years . Varget is no better unless you push it hard . Had no idea N-140 & 50 were so stable . Going to look into getting some 150 thanks .

And... don't forget another very good one is H4350.

 

[Eraser]

Thanks for the info , seems to confirm what's been said for years . Varget is no better unless you push it hard . Had no idea N-140 & 50 were so stable . Going to look into getting some 150 thanks .

Did I read it wrong? It looked like the N-140 was very sensitive.

 

[Tpb10505]

Thanks for the work and info! Didn’t expect N150 to fair that well.

 

[urbanrifleman]

R15. Crazy as a March hare.

Ar Comp once again proves to be a totally different animal and one of the best tested.

 

[BillC79]

Did I read it wrong? It looked like the N-140 was very sensitive.

N140 had low sensitivity between 34F and 66F. It is only when temperature goes between 66F and 97F that sensitivity was measured. If you shoot in cooler climates, you would probably have no problems.

 

[Keith Glasscock]

N140 had low sensitivity between 34F and 66F. It is only when temperature goes between 66F and 97F that sensitivity was measured. If you shoot in cooler climates, you would probably have no problems.

But, I do have to watch it closely as the temps get up in the summer... My 185 Juggernaut load picked up about 18 fps as the temps increased. I have to back it down to get back into the node...

 

[avidflyer]

How old was the lot of N150?? I picked up several 8 lbers dated 2015, been a great powder, but have been told newer lots have a additive in them to be more temp stable.

 

[BillC79]

How old was the lot of N150?? I picked up several 8 lbers dated 2015, been a great powder, but have been told newer lots have a additive in them to be more temp stable.

January 2022 lot number on my N150. The older powders are supposed to be less temperature stable which I confirmed for N140. I don't have experience with the older N150.

 

[chop house]

this post and follow on data yet ANOTHER reason i hang out around here. thanks.