Is powder temperature sensitivity over blown?

[Lemonaid]

A few random thoughts.
If P.T.S. is so bad, why do they make so many double based (ball) powders? What are they good for then?

For hunters/field use, doesn't the likely range of temp. fall between say 30* and perhaps 90*? so the swing from average is only 30*. I would think that variations on target from say 150 fps would make little difference at the ranges most shots will be taken at.

What powders do factory hunting ammo use? Is it always a P.T. insensitive one?

I'm thinking that for most of the time P.T.S. is not a factor, it's only at rare extremes of distance and temperature that an temp insensitive powder would be needed.

I am interested in what your take on this topic is.

[trubulator]

A few random thoughts.
If P.T.S. is so bad, why do they make so many double based (ball) powders? What are they good for then?

For hunters/field use, doesn't the likely range of temp. fall between say 30* and perhaps 90*? so the swing from average is only 30*. I would think that variations on target from say 150 fps would make little difference at the ranges most shots will be taken at.

What powders do factory hunting ammo use? Is it always a P.T. insensitive one?

I'm thinking that for most of the time P.T.S. is not a factor, it's only at rare extremes of distance and temperature that an temp insensitive powder would be needed.

I am interested in what your take on this topic is.

The average deer is supposedly shot at under 100 yards. I imagine it really doesn't matter at those ranges.

Last year I shot a doe at 325 yards. I developed the load in the summer, and ran into the herd in December after a snow storm cleared. The doe was moving and the wind was blowing. Took a few tries to connect. I'd guess I had about a 70 degree temperature difference between when the load was developed and my shot opportunity, on top of a whole bunch of other field variables that made things challenging. So I appreciate a temp stable powder to remove a variable.

I have also been burned by a load workup that I did in cold weather that was fantastic at 30 to 40 degrees, but when I shot it at 80 was all over the place. I can tolerate that sort of thing for target, but not the very few hunting shots I take at big game.

[JASmith]

We all agree that seeing a 100 fps change in velocity is unnerving.

Further, cold days have denser air and hot ones less dense, which adds to changes in drop and drift.

One way to approach the question is to look at reported variations in muzzle velocity with temperature. Then bound the problem by looking at the velocity at 110 F (ugh!) and at 0 F (yikes!).

Then run one's favorite trajectory calculator that includes an option to look at drag at field temperatures and typical winds to determine drop and drift differences at, say 500 yards -- a range that very few people should consider taking a game animal. (Yes, many, if not most, of us on this forum have dreams of being Quincy Down Under, but statistics show most game are harvested at ranges of less than 300 yards.)

That should tell us if it is truly an issue for most of us.

PS A metric for "Good enough" is the 10" circle (Jack O'Connor's canonical dinner plate). Assume one is sighted in to hit the center at the chosen range and then ask whether the bullet drifts 5" or more away at your favorite max range.

Note for calibration purposes, ask yourself how good you are at judging the difference between absolutely still air and a 5 mph crosswind.

A difference of 5 mph crosswind will push a Hornady 120 gr CX with a muzzlecoity of 3500 fps almost 14 inches off center.

That might suggest that velocity changes from temperature variations, while real, may not be the dominant factor in driving the bullet out of the vital zone.

(Looking at the 300 yard drift of just under 5" at 300 yd in that 5 mph wind might also tell us why 300 yards should be our personal maximum range.)

[trubulator]

We all agree that seeing a 100 fps change in velocity is unnerving.

Further, cold days have denser air and hot ones less dense, which adds to changes in drop and drift.

One way to approach the question is to look at reported variations in muzzle velocity with temperature. Then bound the problem by looking at the velocity at 110 F (ugh!) and at 0 F (yikes!).

Then run one's favorite trajectory calculator that includes an option to look at drag at field temperatures and typical winds to determine drop and drift differences at, say 500 yards -- a range that very few people should consider taking a game animal. (Yes, many, if not most, of us on this forum have dreams of being Quincy Down Under, but statistics show most game are harvested at ranges of less than 300 yards.)

That should tell us if it is truly an issue for most of us.

PS A metric for "Good enough" is the 10" circle (Jack O'Connor's canonical dinner plate). Assume one is sighted in to hit the center at the chosen range and then ask whether the bullet drifts 5" or more away at your favorite max range.

Note for calibration purposes, ask yourself how good you are at judging the difference between absolutely still air and a 5 mph crosswind.

A difference of 5 mph crosswind will push a Hornady 120 gr CX with a muzzlecoity of 3500 fps almost 14 inches off center.

That might suggest that velocity changes from temperature variations, while real, may not be the dominant factor in driving the bullet out of the vital zone.

(Looking at the 300 yard drift of just under 5" at 300 yd in that 5 mph wind might also tell us why 300 yards should be our personal maximum range.)

I don't really want to be taking shots beyond 300 yards as I consider that or just beyond my personal limit. Some of that is the aforementioned pie plate consideration, some of it is travel time of the bullet, some is unpredictable winds, etc. Too many things can go wrong at extended distances. In the menatime, the more variables I can control or reduce the impact of, the better. So I choose temp stable powders to cut down on temp changing velocity I prefer high BC bullets to reduce the impact of wind drift. Limit range, etc. Others can shoot farther and I stand impressed, but it isn't me.

[kmon]

For most it is way over blown IMO. The further out you shoot the more in play it becomes. Guys that routinely shoot at 400 yards to a mile or more are very into temp stabil powders. Folks that rarely if ever shoot past 200 or even 300 yards which is the majority of hunters I do not think it makes enough difference to worry about.

If I am working up a load in the cold weather I will opt for a more temp stabile powder, I learned about that with loads that were safe at 30 degrees and right at MAX published data and get a blown primer when shot in July on a 100 degree day with a now discontinued powder. That load in cold weather turned in the smallest groups I have ever shot with a TC Contender.

[EastTNHunter]

I’m more concerned about safety when it comes to temp sensitivity. Develop a load at 40 that’s great (no pressure signs), then start getting loose primers at 95. Scary

Also, temp sensitivity MAY be enough to get you out of an accuracy node in extreme situations. I’m not a long range shooter, but I also like to have confidence in my loads.

[lazyengineer]

I've been burned by it. Win 748 light load with a weak primer in 5.56 Runs fine in the summer. Cold temperature winter and it's hangfires and misfires.

Service rifle shooters can get zinged with ith, and BCL2. Which can have crazy pressure spikes if a casing developed in pleasant conditions is let cook in the sun at a competition match on the 600 yard line.

For a mid-levvel load shooting a deer lung shot at 85 yards? pretty irrelevant.

[AK_Reloader]

Does the copper reducing powder blends help or hinder the temperature insensitivity powders?

Marketing B.S.

[AK_Reloader]

I've been burned by it.
Service rifle shooters can get zinged with ith, and BCL2. Which can have crazy pressure spikes if a casing developed in pleasant conditions is let cook in the sun at a competition match on the 600 yard line.

Cover said ammo w/a Boonie hat & the issue is negated.

[kmon]

Single based powders will be the mot temp stable, add the Nitro Glycerin to it and get more energy for velocity from it but there goes the temp stability.

Higher energy powder will give the highest velocity but at a cost. If hooting for long range go Single base powder with very low ES and accuracy. At 100 or 200 yards you might not really notice a 100fps swing for hunting and I have seen factory loads that would do 3 shot group under an inch at 100 and 200 yards measure over 100 fps ES.

[Lemonaid]

I've been burned by it. Win 748 light load with a weak primer in 5.56 Runs fine in the summer. Cold temperature winter and it's hangfires and misfires.

Service rifle shooters can get zinged with ith, and BCL2. Which can have crazy pressure spikes if a casing developed in pleasant conditions is let cook in the sun at a competition match on the 600 yard line.

For a mid-levvel load shooting a deer lung shot at 85 yards? pretty irrelevant.

I'm unsure if a temp insensitive powder will have better ignition/combustion at low temperatures? If you switched 748 for another powder with the same "weak" primer, did it run fine in the cold? If so what powder did you switch to?
Actual experience is invaluable, my thanks to all who share.

[Harpoon1]

What powders do factory hunting ammo use? Is it always a P.T. insensitive one?

Every piece of Grendel factory ammo I’ve pulled apart has had ball powder in it!

[kmon]

From another forum, the second quote here is from an ammo manufacture I know and he is small time compared to many but does a thriving business.

Do commercial ammo manufacturers ever use powder that is not available to the general public?

Absolutely! I have access to some powders not offered via retail. They also blend powders to come up with a certain burn rate. For example, an ammo company I work with uses a lot of SMP 763, which is Alliant 2000MR powder. They can cater the burn rate of that powder they want from the factory to a slightly slower burn or a slightly faster burn for the application they want for a line of ammo. It's impressive when to see powder when they order it in 50,000 to 100,000 lbs all at once.

[lazyengineer]

I'm unsure if a temp insensitive powder will have better ignition/combustion at low temperatures? If you switched 748 for another powder with the same "weak" primer, did it run fine in the cold? If so what powder did you switch to?
Actual experience is invaluable, my thanks to all who share.

It's a good question, but probably not. The little research I've seen on primers varies from "very little" to "practically none". But I wouldn't call that definitive. Essentially though, those statements do make some sense. The energy content of a primer is released all at once in an explosion. Which has so many KCal of energy release upon the instant chemical conversion of the reactants. That propagation happens all at once, or at least, at a rate that is faster than the shock-wave, which is an explosion. Cold or hot, about as much energy is coming out of that primer regardless - minus the sensible heat effects of the cooler T, which is fairly neglible.

Gunpowder is much more complex, and is a slower reaction. While it too contains a certain amount of KCal's, and upon full reaction, will essentially also release all of it regardless, is true. But Gunpowder is a complex reaction propagation, where the conditions affect the propagation, and the propagation affects the conditions, which can affect the final energy release and extent of powder consumption. Where the reactants are combusting at a rate slower than the pressure wave propagation. The initiation of the reaction requires enough heat from the primer to start the reaction of the gunpowder, and enough of the gunpowder to generate enough heat, to self-sustain propagation. Which is why ball powders are more difficult in cold weather, because a stick-powder has an edge to be immersed in the primer flame, light, and propagate. Spherical powders are smooth and don't have corners to be bathed in flame. So they are harder to start. In addition, a gun powder reaction rate and energy release is dependent on how hot its neighboring molecules were and are firing it up, and how cold it is, and it's other neighboring molecules are, soaking up the heat. Colder powder can have a slower absorption, or straight up insufficient absorption, of the primer heat, and a slower propagation of burn rate while heat is being sucked up warming up the molecules more first, to finally exceed the activation energy to react and light. A slower reaction means less powder was fully consumed in that initial critical first 1-2" of bullet travel, where everything is immersed in the maximum temperature and pressure plasma. Once the bullet gets past this point, the reaction rate is quenched by the bullet travelling down-bore releasing the plasma pressure (and temperature). You can still get some burn, but very little compared to peak Temperature and Pressure rates in those first couple of inches. (Hence, fast powders with fast burn rates for large ratio of bullet diameter to reaction chamber (i.e. pistols and shotguns), vs small diameter ratio to reaction chamber (rifles). If the powder starts cold, and is a composition where it's difficult to light due to heat-transfer properties (i.e. a sphere vs being a stick with sharp edges), and is a composition that has a higher activation and/or heat capacity; cold weather and cold components work against you.

one interesting part of all this is that cold barrels, are actually quite important as well; even if the ammo is loaded warm and quickly fired. Because that can be a heat-sink for one thing, I suppose; but that's what I read.

Or at least, that's how I look at it - not my area of research and expertise, but that's my best explanation on why cold is more important in regards to the gunpowder, than the primer.

[Lemonaid]

No sir, I'm not going into that rabbit hole. Great post, lot to think on!

[stef1274]

Want to add something - hope it helps.

While temperature stability may be good, and temperature instability may be bad, make sure whether your powder is actually stable or unstable.

Test: I read an article a while ago, but I am unable to find it again now. Someone did a test with a number of SB extruded and DB ball powders. The way the guy did the test really looked solid to me. He cooled (with a 12V fridge) and heated (with a seedling heat mat) batches of each, loaded to the same CBTO and pressure rating. He also did some temp increments in between the extremes. Of course he worked with thermometers, good recordkeeping and good principles such as barrel management.

Result: both the SB stick and DB ball had some velocity response to temperature. The variations were quite linear, and relatively small for a hunter's requirements. I can't remember the exact variations, but the article blew away the idea that SB is oh so stable, and DB is unshootable. In some cases, variances on DB ball were actually smaller than its equivalent stick powder, most notably so in my favourite ball powder, Somchem S321.

After reading that article, I became very relaxed around this topic. I know I don't chase velocity, and rarely have loads > Pmax - 15%. I also hunt in areas where 80% of shots are below 150yds, and often at larger animals (read 'larger vital zones'). I only hunt in autumn and winter, and go to the range only early morning in summer, or midday in winter.

Summary: To answer the OP's question, yes, I think temp sensitivity is overblown. Not because it doesn't exist, but because the majority's skill level and requirements are insensitive to it. Also, don't just assume a powder to be stable or unstable just because someone said so. If you really must know, go and test it.

[VASCAR2]

A Friend uses Accurate 2520 and 120 grain Nosler Ballistic Tip for a hunting load for taking antelope in Wyoming. He develops his load at 400’-500’ ASL in the midwest. His hunting area is 7200’ ASL and usually very cold and windy. He has chronographed his load in those conditions and zeros his rifle at those temperatures at that elevation. He has been very successful using a powder affected by temperature.


I read a temperature test using AR Comp and in that test AR Comp showed very little change in velocity at higher temperatures but as the temperature got closer to zero the velocities exhibited the most change. I read AR Comp is manufactured in Sweden and was surprised by the powders behavior at lower temperatures. If I remember correctly as the temperatures got close to zero velocity increased which is usually opposite of powders like Accurate 2520.

I shoot mostly double based ball powders and as I get older the less I’m inclined to shoot in very cold or vey hot temperatures. I don’t normally load to max pressures and try to watch for abnormalities.

[treed]

I hunt in far north Minnesota where we can have temp swings from 70f to -15f all in one season. I hunted most of my life with bolt guns in your typical calibers, 3006 308 260 etc and never once thought about temp stability. Now shooting the Grr out of a gas gun I have fretted about it probably too much. Granted we are not shooting long ranges like some. we are more concerned with reliable function and hunting accuracy. Will a small zero shift affect us, probably not but target and comp shooters a whole different discussion. Just rambling a bit

[LRRPF52]

Here’s a comparison of the 123gr SST with a 100fps difference between 2 loads, the faster one fired at 80 deg F, the slower one fired at 20 deg F:

2460fps mv, 80 deg F, 100yd zero confirmed at 80 deg F:

200yds 2119fps 1226ft-lbs -4” drop .6 mils
300yds 1959fps 1048ft-lbs -16” drop 1.5 mils
400yds 1807fps 892ft-lbs -37” drop 2.5 mils


2360fps mv, 20 deg F, 100yd zero confirmed at 20 deg F:

200yds 1983fps 1074ft-lbs -4.7” drop .7 mils
300yds 1810fps 895ft-lbs -18” drop 1.7 mils
400yds 1647fps 741ft-lbs -43” drop 3 mils

400yds in the latter example is well below the expansion threshold of the 123gr SST.

Both loads are capable of generating expansion with that bullet out to 300yds, with only 2” of drop difference between them at 300yds.

If you use a 50yd zero for both of them, they both maintain a point blank zero placing the shots within a 10” vital zone out to 225yds with no dialing or need for reticle holds.

[LR1955]

Want to add something - hope it helps.

While temperature stability may be good, and temperature instability may be bad, make sure whether your powder is actually stable or unstable.

Test: I read an article a while ago, but I am unable to find it again now. Someone did a test with a number of SB extruded and DB ball powders. The way the guy did the test really looked solid to me. He cooled (with a 12V fridge) and heated (with a seedling heat mat) batches of each, loaded to the same CBTO and pressure rating. He also did some temp increments in between the extremes. Of course he worked with thermometers, good recordkeeping and good principles such as barrel management.

Result: both the SB stick and DB ball had some velocity response to temperature. The variations were quite linear, and relatively small for a hunter's requirements. I can't remember the exact variations, but the article blew away the idea that SB is oh so stable, and DB is unshootable. In some cases, variances on DB ball were actually smaller than its equivalent stick powder, most notably so in my favourite ball powder, Somchem S321.

After reading that article, I became very relaxed around this topic. I know I don't chase velocity, and rarely have loads > Pmax - 15%. I also hunt in areas where 80% of shots are below 150yds, and often at larger animals (read 'larger vital zones'). I only hunt in autumn and winter, and go to the range only early morning in summer, or midday in winter.

Summary: To answer the OP's question, yes, I think temp sensitivity is overblown. Not because it doesn't exist, but because the majority's skill level and requirements are insensitive to it. Also, don't just assume a powder to be stable or unstable just because someone said so. If you really must know, go and test it.

Stef:

Totally agree. I have put issued M-118 Special Ball into a bed of MRE heaters and got them so hot the shooter had to use gloves to put them in his M-24. Also put some on dry ice to cool them down. I did take temperatures using a thermometer. Can't remember the exact temps but there was about a hundred degree difference between the two. Shot them over a chronograph and found about a sixty fps difference. The powder was a ball powder. That's about one minute and yes, it can mean something but that something is caught up in a bunch of 'other things' and in my experience those other things tend to balance out any changes in velocity caused by powder temperatures.

I think some extruded powders of yesteryear had big problems with extremes of temperature but not so today.

LR-55