I am trying to settle on 2-3 powders at most that will work well across the range of bullet weights for the 270WSM, 280AI, 7RM and 300 WM. If they work for other rounds well that's a bonus.

The powders I am looking at are in the range of: R25, RS Magnum, 7828SSC, VV165, VV560, Mag Pro, Retumbo, H1000. Any others I should consider?

How do they compare for temperature sensitivity and lot uniformity? Do any of these have a broader loading application than the others? Do we get too Loony about temp. sensitivity?

Depends on your hunting conditions. I hunt deer a lot (and elk now and then) in pretty cold temperatures, so prefer the most temp-insensitive powders for those uses. For pronghorn hunting I don't really care much, as temperatures are going to usually be within 50-80 degrees, not enough to make much difference.

Even temp-insensitive powders will react somewhat to temperatures much above 80, just less so than standard powders.

Alsom temp-insensitivity depends quite a bit on the cartridge and use. Maximum loads with heavy bullets in smaller-bore magnums will probably show more temperature sensitivity than when the same powder is loaded in, say, a .30-06 with 165's.

In my own tests the Hodgdon Extremes have always done the best, but some others are pretty good these days as well, including RL-17 and Ramshot Hunter and Magnum. The big problem isn't the 100 or even 150 fps, but change sin accuracy and point of impact.

This months Barnes Bullets newsletter has a very nice article/test on that very subject.

http://www.barnesbullets.com/resources/newsletters/july-2010-barnes-bullet-n/

nsaqam,
Thanks for the link. Good article and interesting information.
Test

Unfortunately, they used the too-standard test method of just freezing or heating the ammo, not the entire rifle.

I have gotten very different results when testing that way, and when testing when rifle, ammo and ambient temperature are cold or hot.

There are several surprises there................based on JB's comments, it may be somewhat suspect.

MM

I thought so too.

In other words, you need to be willing to go out there and freeze your ass off?

I prefer to think of it as testing hunting rifles and ammunition under actual field conditions.

Freezing my ass off is, well, often part of hunting!

Come on John... any valid accuracy testing of shooting ammo cold temps should factor in the SHIVERING of the shooter, right???

If I were going to do such an article, I would want to run tests on loads after significant actions -- carry the rifles and ammo on horses for four hours on sub-zero days, then pull them out and test some loads. Or drive them around in a truck cab for four hours, get out, sling the rifle, hike four miles with it at low temperatures, unsling it and fire test rounds.

Wouldn't be too hard to some up with some tests and run them. I have a suspicion some of the outcomes might be somewhat different than tests at the shooting range, no matter the temperatures.

Dennis

Well, yeah!

Oddly enough, however, shooting at around zero isn't that bad. I pick a days when the wind isn't blowing, and since I grew up in Montana I know how to dress for cold weather. I also have my pickup truck (with a warmed-up engine) within 20 feet of the bench at either of the ranges I use--but don't remember ever having to get back inside, partly because I'm usually hiking back and forth to the target every few minutes.

John,

Have you had the chance to test Hybrid 100V for temp sensitivety?

Got a pound sitting around I haven't loaded yet. Here in TX temps propably doen't matter much, except the extreme heat.

Just curious.

Thanks,

Bill

proving once again than nsaqam is the "internet theorist nincompoop" that he is so often accused of.

I shoot year round up here, 90 above to -30 below on occasion. Velocity changes for a variety of powders, regular types and "temp insensitive" types and have not noticed much difference between them. I seem to get more velocity swing when the temperature goes from normal 65-70 degree days to really hot 90+ days. Havent noticed all that much velocity loss from normal summer temp to the dead of winter, maybe 50-75 fps. Not enough to concern me. My biggest challenge when it's 30 below is keeping chrono batteries warm.

Here a study that has some info.

http://www.shootingsoftware.com/ftp/Pressure%20Factors.pdf

tx270,

I've only testing H100V in cold weather, in one cartridge/bullet combo. It's definitely not one of the Extreme powders. Velocity was down a lot and it showed on the target as well. It might act differently in warm weather and/or a different combo.

This is exactly what I found last Winter testing loads at 400 yards.

Loads worked up in 40-70 temps didn't do so hot in the accuracy dept when it got below about -10F. They went from roughly MOA to 2MOA. Didn't see much of a difference from about 10-50F. Powders tested were H4350, R17 and H4831SC. H4831SC actually performed the best, very little if any loss of accuracy/POI.

Which is one reason a lot of my cold-weather hunting rifles are loaded with H4831SC.

FMAO, with the firearm and ammo:

Thinking -0 Montana wind chills, versus my my puny minus 10 & 20 windchills here.............
.............you da' man, !

I got to go warm up my 'creaking' parts very often when I do it from the bench. Yes, cold/or hot rifle and ammo, some real surprises sometimes. The surprise can be good or, not so good.

Guys - Thanks for the H4831SC tip! Haven't tried that one for 'cold' rifle yet.

Sam Olson - Can you tell what cartridges you tested at 400 please?

JB,

Thanks for the good info.
We use H-4831SC exclusively in 7mm Magnums with no problems in cold weather in the UP.
As a test engineer, I could not accept warming a bullet, then stuffing it in a chamber at zero degrees F and expect valid results, or visa versa.

Thanks for the UP info. Never can have enough data!

Warming/cooling ammo only has always sounded like a weird way to do it. It would especially be suspect when testing primers, because a primer would start warming or cooling the instant it touches the bolt face. I mean, how thick is a primer cup?

OP

for those cartridges I would get some RL17 and some H4831 and never look back.

Good info. The last sentence in the second study sums it up, "it raises more questions than answers". Looks like most of the previous data is suspect.

Where I am concerned is those 100 deg. days where the ammo might get as hot as 120 in the sun or trunk of a car. I try to keep it in a lunch cooler under those conditions. I don't do much cold weather hunting these days but when temps are in the teens I keep extra ammo in my inner pockets closer to my body and switch it out every hour or so. Probably doesn't accomplish much.

Makes me wonder about those red line 270 WSM loads including the factory ones.

I tested H4831SC in my 270WCF.

H4350 in a 257 Roberts and a 300WSM.

R17 in two 300WSM's.

Like I mentioned, H4831SC worked very well when it got below 0F. The H4350 and R17 loads lost some velocity(50-100fps?, don't have my notes handy) which is no big deal except for the fact that POI was several inches lower and group size had nearly doubled to 2MOA(8" at 400 yards).

Inside of 300 yards I wouldn't worry but won't be taking any shots much further if it's real cold outside. I guess if it's cold I'll take the 270 but will probably just sit inside and drink whiskey and watch football instead.

It's not fun gutting out deer when it's -20F, made that mistake once, never again.....(grin)


And like you guys said, you're good to go from roughly 5-85F which covers 99% of the hunting here in Montana.

Good question. But wouldn't the giant mass of brass, powder, lead and copper buffer the primer from warming or cooling to whatever temp the bolt face is if the shot is taken a few seconds after chambering the cartridge?

The priming compound is up against the bottom of the cup, the thin sheet of metal that is right against the bolt face. While the head of the case no doubt does tend to keep the primer cooler, I can't believe that the priming compond doesn't start to warm up the instant it touches the bolt face.

It isn't really scientific in data collection, but it is actual experience that I have found H 1000 Extreme to work over the temperature extremes in Montana. The antelope was in 50+ degree weather at 650 yards. The elk at below zero temperatures at 450 yards. I never questioned the rifle's ability at either animal at either distance. I chose the Extreme powder to accommodate that type of hunting with a 300 Weatherby.

H1000 is also a good one, from what I have seen as well. I run it in the 6.5-06 I use for longer-range varmints, pronghorn, etc., and so far it hasn't shown any noticeable changes out to 700 yards, though I haven't tested it in super-cold weather yet.

Silly Mule Deer; don't you remember? Properly-seated primers are below flush with the case head, so they don't touch the bolt face at all!

Seriously, though, one of the questions raised by the studies linked is: Are the 'temp-insensitive' powders merely coated with an easy-lighting substance?

One thing to remember is that powder lot# vary in buring rate, re-test different lots or buy of the same lot#, especially if you are shooting load at a Max load or just below Max.

It's a bad deal to be on a hunt, and sieze the bolt up in your rifle....lesson that I learned while on a deer hunt in Utah. I shot just underneath the belly of the buck at 400, and could not get the bolt open for another shot....buck just stood there and looked at me!

Pressures skyrocket at temps below Minus(-) 25 degrees.

h1000 is what i use in my 338 ultra and 257 roy works great

h1000...very little deviation....best i have found

In my cold weather testing in Minnesota, my logbook shows that 3 powders have been my most consistent - Varget, H4350 and H4831SC.
I have used these 3 powders for: .204Ruger, .223, 7x57, .270Win., .270WSM, .308, 30-06, 300WM, 300WSM, 338WM and last but not least, the 375 H&H. I feel I have not short changed myself on performance and the consistency from 0* to 80* on my chronograph and the logbooks back it up. Also, it simplifies powder purchases to 8 lb. kegs. This system has kept me from trying the new powders of the last few years but I am happy with with what I have.

I remember doing that quite a bit growing up in Montana. -30 on Thanksgiving day in the mountains around Eureka or above Trout Creek. I'm a sissy now. Southern Idaho is warmer.

It is indeed! My mother has lived in Boise for over 40 years now....

JB,
Is there any meaningful difference in temp stability of Ramshot's TAC vs. X-Terminator? TAC works well in my 338 Fed, but it appears X-Terminator might work even a bit better with the lighter bullets.

In my experience TAC is noticeably less temp-sensitive. In my very first cold-weather test of TAC, in a .223, the same load chronographed EXACTLY the same at zero F. as it did at 70. Now, that would be highly unusual, even when chronographing the same load twice in one day, but still....

My question: What do you mean by X-Terminator working "better?" Does it get 50 more fps? Or does it group 1/4" tighter at 100 yards? Is it enough better to make any difference to a deer?

In my cold-weather hunting loads I'm very willing to give up a little accuracy and 100 fps of hot-weather speed for consistent performance at any temperature I may be hunting in.

Well, 'better' is a highly variable notion that I'm free to change on a whim depending on what seems important at the moment. Yesterday, 'better' meant faster. However, it's also related to the fact that I have not been able to get 180 BTs to shoot very well with TAC. Ironically, TAC is my go-to load with the 185 TTSXs. Quite pleased with it there. I most likely just need to fiddle with the TAC/180BT load more to find a sweet spot. Looking at the Ramshot load data, X-Terminator was, as you noted, about 50FPS faster than TAC (but also at a higher pressure, ...maybe just add a touch more TAC and equal FPS at same psi?). So, I was thinking I may try it, and if I were to get the 180s to go faster and be more accurate that would be "better". I would not try X-Terminator if it is significantly more impacted by temps. Shooting near 100deg this week, will be shooting well below freezing in the winter. I do agree that accuracy trumps all. It is my search for accuracy (and just curiosity) that leads me to consider trying X-Terminator. ...or maybe I should try IMR 8208 XBR?

I also wonder if the change in barrel harmonic is a factor in very low temperatures changes point of impact? Both due to velocity change and metallurgical changes.

Elasticity, expansion, hardness, bore diameter, and other things would change very slightly with extreme temperature shifts. I would discount this except for the photos of blown stainless steel barrels in very low temperatures confirm something is changing.

I have found Retumbo to be fairly tem stable. At least down to 10 degrees.

MD and friends,
My experience mirrors that of Bigwhoop with H4831sc being my top cold weather performer down to -10 which is about as cold as it has ever gotten here. Currently, I am playing around with AA2230 & AA2250 in .223 and other sub 30 caliber rounds vs Varget in different temperature extremes. So far Varget is better in heat but I still have to do the cold weather tests for each rifle this winter.

Flower Child

How stable is Varget in hot/cold swings?

I wonder how Varget and RL15 compare in cold... I've hunted with my 308 in -23F weather stoked with RL15 and have always wondered about it but have never tested it... I'm not as motivated as Sammer (grin).

Just looked over the Barnes article... seems, at least within their testing parameters, Varget is quite a bit more temp stable than RL15...

I have used it in my .308's up here in temps as low as minus 40F with good results....even at long range.(MV has stayed consistent)

Brad, didn't hear the phone ringin' in the tractor, just got your voicemail. I'll be up here for another week or two.

I've tested Varget down into whatever temp that 9V batteries no longer work. 46 grains of it under a 165 Hot-Cor still goes 2740 It goes closer to 2780 if you leave your loaded rifle on the dash in the summer.

Of course I buy Varget by the 4 pack of 8 pound jugs so I can deliver this kind of info to the Campfire (that and I don't have to guess if 40 FPS swings over the year are caused by different lot #s)

LMAO


Only in Montana

A couple weeks ago I spent a day at a pressure lab, and the guy I interviewed said that Varget typically acted very reliably in the .308 Winchester at extreme temps, but when
"stressed" (the word he used) it could get a little wonky. The specific example he used was the .260 Rem. with a 140 at top pressures, a place where a somewhat slower powder would work better.

Which goes along with what I have found in cold (and heat) testing over the years: The particular case and bullet can affect how well a certain powder is resistant to temperature change, yet another reason to actually test our loads in the temperatures we might encounter when hunting.

Ha, too true!

Sammer, I'll be down at the ranch during the week but home weekends... give a jingle when you're in town.

BTW, ran into a Sow grizzly with two cubs in tow making a kill on an elk calf a few weeks back... was pretty exciting (grin).

DakotaDeer & Brad,
The only way to know for sure is to do the work. As MD hinted at, powder is just one variable to the equation among at least 10 others that I can think of, which makes for a lot of miserable combinations to test. Once in a while you get lucky and find some that shoot well in a variety of conditions but usually this is not the case. I have a whole shelf full of loaded ammo marked for different temps, climates, and conditions for specific rifles. Then I have a bunch of GP ammo that I use for everything else. I always seem to have something on hand that fits the bill but only rarely do you find a load that does several different conditions well. Consequently, my rifles are divided into three temperature extremes -10 to +30, +30 to +60, and +60 to +105 all of which represents the spectrum of temperatures where I live. This is not to say that I have a lot of rifles, but rather that through experimentation, I have found a lot of loads for them that work under certain conditions.

Flower Child

You are far more "into it" than I am FC. I like to find one load that I can use everywhere. Now, I am guilty of using different bullets for different critters.....
Don't even like to do that. Hard enough to keep my rifles stocked with enough good, reliable ammo. E

The biggest problem I encounter with this is I don't hunt near where I live and conditions can vary greatly between the two locales. The only real cold weather hunting I've done is a winter cow elk hunt in the '05 to '06 season at an elevation of 9,500+ feet. In the morning, getting out of the truck, the temps were usually between -12F and -6F and probably got as warm as the high teens or perhaps low 20's.

But nearer to where I live it's not common to get below zero but temps in the teens and low twenties are typical in the coldest months. The stars would have to align just right for it to be one of those cold weather clear (and not storming/blizzard) where I can also get to the range and validate POI and chronograph results.

I like the idea of it all, but most of my hunting conditions are 40-65 degrees without all the extremes. I sometimes wonder if I worry too much about something that largely doesn't affect me...

John, not to get off topic, but have you ever tested any of the black powder substitutes such as Pyrodex or T7 for velocity change/POI change with temp drops ?

No, not really, because when I shoot black powder guns (whether my T/C Hawken or cartridge rifles) I use black powder. Odd, I know, but there it is....

I understand as I don't consider my Knight in-line a primitive weapon either. Thanks anyway.

Which load should I take when I expect the temperatures to be anywhere from 10 to 50 all in one day's hunt, or from 0 to 60 in few days' hunt?

FWIW - To get 185 TTSX's under 2.82 OAL in my Kimber Montana I had to trim the case to 1.995" - a little short by most books. If you are not shooting a Kimber, you might have that problem. Working with the 185 TTSX's I have not had good luck with X-terminator, High SD's, poor accuracy, low velocity. Just worked up some TAC, got the velocity - but not enough data on accuracy. 8208 is some fantastic stuff, should easily cut your SD's in half, pretty easy to get top velocity in the .338 Fed, accuracy in my gun is good (not great). No change in velocity from 40-85 deg (no cold weather data yet).

Just saw Alliant released its 2000MR, supposedly the same stuff as in the factory .338 Fed ammo. Published velocities are the best for the .338 Fed yet (in a quick glance). Anyone tried it?

I've learned that one way to discover how cold your hands truly are is to "burn" them by poking them in the steaming guts to warm them up. Yow. (But warm guts are one's friend when working on game in the cold. I never carelessly cast them about until the gloveless cold chores are complete. )

Some info here:
Thread

In summary, based on very limited experience, I've run out of space in Federal brass before I hit pressure. Velocities have been good, but not better than TAC in the 185 TTSX.

I find this to be the simplest explanation, and also the one which best explains the extremely variable results. I refer here to how some loads will exhibit let's say an 80 to 100 fps difference and have a half inch change in POI. Another load will show about the same velocity difference, but POI will move inches in 2 different directions. That's a clear harmonics issue, to me. In essence,then, the original load may shoot well, but it's a 'fragile' load in that a tiny change in anything at all will destroy its performance.

All of us have had the experience of accuracy AND point of impact changing noticeably when working up loads with some rifles--while in others point of impact remains very similar even with varying charges of the same powder. Often the most consistent rifles have heavier barrels.

In my experience, the same rifles that show wide variations in point of impact when working up loads at, say, 70 degrees, are the same rifles that will change POI at different temperatures--unless loaded with very temp-stable powders.

I agree with your observation that thinner barrels will usually whip more, and I also agree that managing variables can be more important for some rifles than others. Where I think we disagree is on the universality of the notion of temperature stability of a given powder (see the Bramwell article), and therefore the confidence one should place in such claims/notions, and also about how much explanation or discussion is warranted when we talk about the various factors that impact POI.

I haven't read the Bramwell article yet, but I don't place absolute faith in temp-stability claims of any powder--and have posted to that effect many times, because of my own test.

In fact many powders will vary in their temp-stability depending on the specific cartridge and bullet, which is why I have also advocated test-shooting at the temperature you might be hunting at no matter what powder you use.

H4831SC, however, has tested well so many times in varying conditions, and in several cartridges, that I do tend to place a lot of faith in its ability to deal with temperature changes, especially cold.

MD,

Do you know if "regular" H4831 mirror this charactoristic of the SC version?

DakotaDeer,
Where are you? The Dakotas? Given the question as posed, I would recommend taking a 20 rd box of both temperature ranges and a small wind guage with a built in thermometer. Barring that take a box of the lower temperature range and hunt early morning and late afternoon with a break in between to enjoy nature and rest up for the late afternoon to dusk hunt.

Flower Child

SOTG,

Hodgdon claims it does. I haven't any regular H4831 in a long time, though, so haven't tested it.

Thanks, was wondering as the last time I made a trip to Powder Valley they were out of Short Cut and I had to buy the Original. OTOH it rarely gets that cold down here during deer season and if it did I'd probably follow Sam's advice and set in the house, crack open another Smithwick's and wait until the next day when it would likely be 40.

Can't hurt to start with the powders that have proven themselves even in dubious tests. More field testing needed.

But I am still going to retain the right to claim the first shot was just a warning to alert the game to be more sporting, the second is to warm the barrel properly, then the third is all business.

Do you still use a regular drop measurer? If so, I think that leaves two of us.


Travis

I noticed this years back when I used to use IMR4831 extensively in both the 270 Win with 130 gr bullets,and the 7RM with 140's;the powder showed greater velocity losses in winter temps(below 20F) in the 7 RM than it did in the 270 Winchester,in which it was pretty consistent....for some reason...

Has any one used H4831SC in the 257 Roberts? I thought to try that as from this discussion H4350 is a bit more temperature sensitive?

Travis,

Actually, I know quite a few handloaders that still use mechanical powder measures--including most of the gun writers I know--and for very real reasons that I ain't going into here.

jimmyp,

In my own tests, H4350 has performed very well in cold temperatures. I first tested it in the 7x57 with 140's. At 70 degrees the load chronographed 2842 fps, and at zero it chronographed 2832 fps. Point of impact was unchanged, and in both tests the rifle grouped three shots under an inch.

I also perform temp-tests every time I go to the range, noting the temperature that day in my loading notes. I regularly shoot in temperatures ranging from 25 to 90, and H4350 has performed very reliably in that range.

As I've pointed out earlier in this thread, even temp-insenstive powders will vary in performance with the cartridge and load. In particular they can get a little wonky if loaded to the ragged edge of pressures, especially in a cartridge where a little slower powder might work better. The primer can also make a difference in really cold weather (and here I am talking about tests done with everything cold, not just the ammo).

At any rate, if you're really worried, H4831SC does work very well in the .257, especially with 155-120 grain bullets, though it also works pretty well with 100's.

I'm a Redding BR-30 user. For big charges I throw half twice.

Which is still quicker than any electronic measure I have ever seen.

It's also hard to use an electronic powder measure on a progessive loader....

Mule Deer,

You (and others) mention that the temp. sensitivity varies with the cartridge. Have you ever done any testing with the 6.5x55? If so, what powders stood out there?

H4831SC works very well in the 6.5x55, and as mentiond earlier in this thread is one of the most reliable temp-resistant powders. I've also had great luck with H4350, especially with bullets in the 120-grain range, even in very cold weather.

This is a very informative thread. It prompted me to finish a hot vs. cold test I started two winters ago.

The two best loads for my 26" 257 Weatherby with its most accurate bullet, the 117 gr. Hornady SST, use IMR-7828 (68.5 gr) and Ramshot Magnum (73.0 gr). Using Fed 215-M primers and an OAL of 3.190 both loads give sub-MOA accuracy with velocities in the 3300-3350 range (at normal temps) and nearly endless case life in Norma brass.

In an effort to find out which load was the "best", I loaded one lot of cases, half with each powder, and shot half of each through the chrono on as cold of a day as I get here (32 degrees). Then I set the rest aside to wait for a hot summer day. This thread reminded me of my test so yesterday I broke out the ammo and shot the rest through the chrono at 92 degrees. Here is what I got:

IMR-7828 SSC (68.5).... Ramshot Magnum (73.0)
92 degrees 3370 fps.... 92 degrees 3354
32 degrees 3318 fps.... 32 degrees 3285
difference 52 fps.... difference 69

IMR-7828 SSC came out the winner but you can see that both of these powders did pretty well. I should add that POI did not seem to change a noticable amount. Other testing with these two loads at long range since I fired the cold string had given the edge to the IMR-7828 SSC, since it grouped about one inch smaller at 400 yards than Magnum did (3 inches vs. 4 inches).

This rifle, a Mark V, made me a believer in Ultra Bore Coat, and it was a two-MOA rifle until I gave up the free-float and added fore-end pressure. I credit JB for much of the success and enjoyment I have gotten from my shooting from his articles and sharing his knowledge on this forum.

As to velocity loss with lower temps, I read an article once that gave a rule of thumb: "On average you will gain or lose one fps for each degree of temp change". I don't remember if the writer was talking about any particular group of cartridges or powders. Since I do lots of testing and almost every round goes through the chrono with the temp recorded on the data sheet, I have found this rule of thumb to be fairly true with the guns that I shoot at relatively moderate temperature. I also learned when you arrive in Montana for your hunt and the temp is near zero you had better confirm your drop figures by actually shooting at the longest range you honestly want to call your limit. I also learned those big Montana critters in that clear air in wide open spaces can be a lot further away than you think. And a relatively flat shooter like the 257 Weatherby won't make up for poor judgement. Thank you, JB, for helping keep me steered in the right direction.

You're welcome!

So, a Montanan should shoot in temps between -20 and 80 degrees.......





If he plans on hunting opening weekend

Yep!

JB thanks for the reply. I love H4350 but the H4831SC is going to get a try as well! If it shoots as well or better I may switch.

So, Mule Deer, if a guy were to buy a #1S in 300 H&H, would H4831SC get the nod ahead of H4350? Purely hypothetical of course.........

This is indeed a very informative thread, thanks for all the information!

I vote it be sticky-fied. What do you all think?

bigwhoop,

No. I'd probably try both and choose which one shot best.

By the way, I bought a 1-S in .300 H&H and Ramshot Hunter got the nod.

MD,
Ok, thanks very much. Still pondering the purchase.

Some good info, Thanks.

Nifty-250 interesting that 7828 came out slightly ahead of Magnum, I would have bet on Magnum. I am curious how R25 and H1000 would come out in that comparison. I always thought the bigger the charge and the slower the powder the more likely that variations would occur. Probably another myth generated from using lots of old H870.

Inasmuch as it's a problem that I have never encountered, or perhaps ignorance is bliss and I never knew I had a problem it has not been a concern of mine..I have shot a lot of the powders mentioned without incident as far as I know..I wouldn't swear to it but I believe that most gunnuts create problems and many of them strive on them, and hey thats OK too...

Very late to this thread but I thought a historical persepective might be useful. Hodgdon rebadges many of the Astralian made powders, designated AR here in Australia and now owned partly by the French company Thales.

Anyway ... when originally conceived ... the design feature being sought was chamber pressures below 48,000cup in 7.62mm ball rounds at 80degC (conditioned temperature ... ie the ammunition was at this temperature not 80degC ambient) which was a temperature deemed as ordinary daily radiation in outback Australia.

What ADI (Australian Defence Industries) is said to have achieved, is the means to control the 'included microporosity' of the powder kernals. Granules have microscopic cavities that were said to be roughly spherical and from 5-20 microns in diameter, smooth and isolated from each other. Hercules are said to have been the first to discover 'microporosity', but the Mulwala (name of the ADI complex) team led by Alister Wylie are reportedly the first to have discovered a way to manipulate and control it. Not sure about now, but at the time it was a Trade secret ... which probably explains why the Australian Govt sold it to the French. The original claim was 'improved progressivity', that is more velocity for lower peak pressures and little effect of temperature on ballistic properties when compared to IMI-type and Ball powders.

The Malwala team were also said to have determined a relationship between pressure and conditioning temperature and expressed it as a coefficient. Whilst Ball powders display a positive coefficient, particularly at above 50 deg C temperatures, the Mulwala team determined how to manipulate the powder to give positive, neutral and even negative coefficients. The 'AR2206 type' powders (of which the Hodgdon sold powders are derived from ... AR2206 was itself derived from numerous tests of a precursor we knew as AR2201) were all manufactured (and I presume still are) as slightly positive coefficient.

Note that at no time was any claim of 'temperature insensitivity' made and that may be a marketing play. No claim that I can remember was ever made to how it would respond to extremes in conditioned temperatures either. We simply know the AR powders as being minimally affected by temperature variations. And some are known to vary considerably from lot to lot ... but that's another story.
Cheers...
Con

Con,

Thanks for the very informative post.

I prefer to call these powders temperature resistant, rather than temperature insensitive. I have found such powders in general to be much more resistant to cold than heat, but still better than older powders in both directions.

There have also been big advances made in ball powders in temp-resistance in the past decade. I just visited with a company that deals in such powders and got some interesting specifics about how they are made.

Thanks for that very interesting post, Con.

FWIW, I shot some more R17 through my WSM's this evening. Temps/ammo/rifles were around 85-90F degrees. Primers were a little flatter and POI was roughly 2-3" higher at 400-490 yards which is no big deal.
R17 appears to be a very good powder.

A possible article on the subject in the future?

Yeah, I have some powder/pressure articles in the works.

That would be interesting. I'd like to better understand the science behind newer powders. It's not like they are leaps and bounds better, but there does seem to be some meaningful improvements in velocity & consistency in the powders available to the reloader as of late. That's my perception anyway.

MD - I would really like to see the articles. Since dropping Wolff, I'm trying to keep track of you - can you let us know where they will be published? Thanks.

I've got some stuff planned for American Rifleman, Varmint Hunter and Guns--but I am also writing for Wolfe again, so will probably do something for Handloader too.

Just when I`m trying to shorten the magazine list you come out a reason to keep buying a half dozen of them......Glad to see ya back at Wolfe.