Temp sensitive powder

[DoTheDew69]

Please explain the effects of temp sensitive powder and temp swings. I'm new to reloading and don't want to blow anything up lol

[outbreaker]

I do my load development during the summer, so when I see temp swings it is in the winter and some like BLC-2 I have seen the velocities drop enough to cause a 8" POI shift at 100yds when the temps get into the 20s.

[A5BLASTER]

Please explain the effects of temp sensitive powder and temp swings. I'm new to reloading and don't want to blow anything up lol

When loading with powders that are known too spike aka temp swing. It's best to wait till it's good and summer to work up a load.

If not then when the summer temps hit mid 80's to 90's it might swing so hard that I will become a dangerous load.

Reverse of that is come winter the load might fall apart and not group well and be much slower.

This is why I'm moving away from h335,cfe223,leverevolution, ppv and probably mr2000 and aa2520.

I have done started reworking my loads with h4895,ar-comp, h322,varget.

These are just some of the very temp stable powders that will work in the grendel.

[grayfox]

"Temperature sensitive" refers to how much gain or loss of velocity a round with that powder will have, per degree F of temp. So if a powder is sensitive, that usually means 1.0 ft/sec per deg F muzzle velocity (MV) or more.
CFE 223 powder is listed in several places as being 1.0 ft/s/*F, Varget (not very sensitive) is more like 0.19 ft/s/*F. RL-15 is 1.52, very sensitive.
So for example, if you load rounds at 72 *F (as in your workshop) with CFE223 at a "max" for you barrel then go outside to hunt in 20 *F winter temperatures, you could expect a drop of about 50 ft/s in your MV... So a 123 gr bullet that you think would shoot at 2475 ft/s (what you loaded for, max for your gun) might actually fire off in that wintry weather, at 2425 ft/s. Your point of impact, downrange energy, ballistics and even accuracy might well suffer because of that drop in MV.
Or, load it "safely (you think)" at 72 *F then go out to shoot in 110 *F summer weather... The resulting load could be too hot and have an overpressure situation due to firing at a MV of ~2500 ft/s... which could be too much for your barrel.

[glk45]

When loading with powders that are known too spike aka temp swing. It's best to wait till it's good and summer to work up a load.

If not then when the summer temps hit mid 80's to 90's it might swing so hard that I will become a dangerous load.

Reverse of that is come winter the load might fall apart and not group well and be much slower.

This is why I'm moving away from h335,cfe223,leverevolution, ppv and probably mr2000 and aa2520.

I have done started reworking my loads with h4895,ar-comp, h322,varget.

These are just some of the very temp stable powders that will work in the grendel.

I'll agree with you on the AA2520. Missed a broad side coyote at 110 yards last week. Aimed center mass complete miss. Had the gun zeroed at 200. Put up a target at 200 shot 10" low. Back to the loading bench. Developed that load last august.

[TomSawyerNW]

Does anyone know the kind of powder some of these commercial ammo producers use? I don't hear about these temperature swings with their ammo like I sometimes read in forums where people do their own reloading. I've shot some of the commercial ammo during summer and winter and don't experience this, or at least it doesn't seem like I do.

[A5BLASTER]

Does anyone know the kind of powder some of these commercial ammo producers use? I don't hear about these temperature swings with their ammo like I sometimes read in forums where people do their own reloading. I've shot some of the commercial ammo during summer and winter and don't experience this, or at least it doesn't seem like I do.

They use powders that are specially formulated and not available to the consumer market.

And yea you can get high and over pressure factory ammo.

Case in point was shooting some hornady AG nice and smooth shooting, no pressure signs and then bang ejector swipe on a case. That tells me that round was a bit overloaded.

[Rosecrans1]

"Most" factory loads are pretty temp stable are are very proprietary. I've seen some Remington Core-Lokt in 300 Savage shoot a little off in the past from a warm September day to a cold December day in Pennsylvania. Where I noticed temp effects the most were on 22LR rounds from Summer to Winter.

[Mikey7373]

Would 8208 be considered temperature sensitive , or is there a chart somewhere that lists all that information.

[BobinNC]

Would 8208 be considered temperature sensitive , or is there a chart somewhere that lists all that information.

http://www.predatormastersforums.com/forums/ubbthreads.php?ubb=showflat&Number=3170475&page=2

[TomSawyerNW]

Thanks for comments about factory loads, A5BLASTER, Rosecrans1. I'll start paying a little more attention to my experience during hot versus cold shooting days.

[LR1955]

I'll agree with you on the AA2520. Missed a broad side coyote at 110 yards last week. Aimed center mass complete miss. Had the gun zeroed at 200. Put up a target at 200 shot 10" low. Back to the loading bench. Developed that load last august.

Gk45:

With 2520 some documents say the velocity changes one fps per one degree F of powder (not air) change.

One minute is about 50 feet per second. So one minute is a powder temp change of 50 degrees F.

And you shot five minutes low at 200 yards. Which equals about a 250 degree difference in powder temp.

Something tells me that your shooting five minutes low at 200 was not due to changes in powder temp.

LR55

[Lemonaid]

Another factor is the firearm temperature. Guns and Ammo TV just had an episode where they took an AR and chilled it to -20 (I think) and measured velocity, then at around 70, then heated the rifle to 140 (I think). Ammo was left out of the chill/heat test.
Got around 100 fps difference from cold to hot just with the firearm temp change.

[Kswhitetails]

Gk45:

With 2520 some documents say the velocity changes one fps per one degree F of powder (not air) change.

One minute is about 50 feet per second. So one minute is a powder temp change of 50 degrees F.

And you shot five minutes low at 200 yards. Which equals about a 250 degree difference in powder temp.

Something tells me that your shooting five minutes low at 200 was not due to changes in powder temp.

LR55

I have to agree here. Those that are seeing more than 2" difference in POI at 200 aren't getting that result because of powder temp sensitivity. There's something else going on.

8" at 100 isn't even believable...

[FRB6.5]

A friend experienced a similar radical POI shift this past Sunday, his Vortex 1-6 had given up the ghost. Minor adjustments made radical changes and sometimes not even in the correct direction. Something worth looking at.