Home Forums Hunting & Shooting Ask The Gunwriters Temp. Sensitivity Chart?

For hunting rifles, I am not one to get real hung up on the temp sensitivity thing. I simply sight in under same conditions as rifle will be used. Or close to it.

However, I have probably around 30 different powders on hand and am considering weeding some out. How clean it burns, how many guns I use it in, and yes, temp. sensitivity all influence my decisions. The latter only somewhat, but it is what has me thinking.

Through the years I have seen various powder charts listing different temp. sensitivities of various powders. These charts all seem to vary from source to source. Same with info I have read from seemingly credible sources, like people who actually work in the industry.

My question is this:

Is there any chart/info that is considered the definitive source or industry standard? One that states Powder X varies ______fps for every degree of temp. change in a given cartridge under a given temp. range.

Like I said, I have seen such charts, read info from powder company people, bullet mfgs., match shooters, etc., etc. But is there any one set of data that is widely accepted as the industry standard reference?

That's tough to produce. Temp sensitivity of the same powder will be different in 2 different cartridges. It's not stabdard across the board like a burn rate.

Even burn rate isn't standard across the board. Powders can switch burn-rates depending on the application.

Learned something new. Thanks!

MD, I was looking in Your BB of GG for 7x57 175gr. NPT loads and saw the H4350 info. Here there are only AA4350 and I4350 available. Are either one of them MOL "temp. insentive" similar to the H? I have a moose permit in NE Wa starting Nov. 1 and was just curious. Thanks-Judd

Both IMR and Accurate 4350 are pretty good in cold weather--not like H4350, but not bad either, which is true of most single-based, extruded powders.

However, temperature sensitivity is irrelevant for quite a bit of big game hunting. Moose hunting would be in that category.

That made me question the importance I've been putting on it. What ranges does temp sensitivity hit your radar?

Depends on what I'm shooting, and what effect it has. One thing most shooters don't realize is that cold not only has an effect on velocity and hence point of impact at longer ranges (which is also affected by colder air during the bullet's flight), but point of impact even at 100 yards.

If your particular rifle tends to result in significantly different POI's at 100 when working up a load, then it's likely to change POI in real cold with the SAME load. How much depends, but I've seen two big game rifles that changed POI three inches at 100 yards when shot at zero Fahrenheit after being sighted-in at 70 degrees. That amounts to a 6-inch change at 200 yards and 9 inches at 300, which can be significant even on big game.

Powders that provide similar velocities in cold as at 70 don't do this. Or at least I've never tested one that did.

Yep. Have seen many POIs be low in cold conditions. That is why I would sight in in the cold conditions or whatever conditions I plan on hunting in.

It would be a complete waste of my time to do final sight in on my muzzleloader, which I only use in December, during summer months or even right now. It would most assuredly hit low come December. I just switched scopes on it and sighted in dead on at 100 yds. Once it gets cold, will do final tweaking......

That's always a good idea--but the shifts I've seen aren't always low. They're often sideways, and in fact one of the 3-inch shifts was almost totally sideways. The load still grouped well, just in a very different place. One even landed two inches HIGHER at zero.

If you watch the movie "Ice Station Zebra", there is a moment when someone declares that an M-16 hits the same place in the cold as it does anywhere else. I remember disturbing those around me in the theater with my disagreement.

Hmmm. And you feel the side shift was due to temp. change alone?

With rifles, I always attribute low hits to the cold when it happens. I cannot ever recall blaming temp. alone for a sideways shift, but that is interesting. Usually I just have to correct elevation, not windage.

I could see it on a wooden stocked rifle before a composite, for obvious reasons. And I do tend to leave the wood at home in extreme conditions.

What I have noticed is that some of my large handguns seem to shift not only low but also sideways in the winter months. But I always blame it on something else like the scope or mounts, wind, or it got bumped, or the brutal recoil, or my shooting. Never really thought about it being the temperature. I will say that H110 is definitely not the most insensitive powder.

Interesting. I can wrap my tiny brain around cold causing low hits, but why would cold alone cause sideways shift? Steel swelling, changing harmonics? He11 IDK, haven't given the sideways thing much thought......

The more I read into things like this, the more I think I'll move to a single main hunting rifle. Much easier to keep sufficient data logs.

2muchgun,

I normally (but not always) run temperature tests in fall, because between mid-October and sometime in November the temperature in Montana will be 70 during a few afternoons, and down around zero at night. The rifles used in the tests usually (but not always) have synthetic stocks that have proven stable, along with scopes that have proven to be the same. The rifles with wood stocks are epoxy-bedded and free-floated. I don't take the test rifles out hunting during the interim between the warm and cold tests.

In fact I don't even fire them, clean them, or otherwise dick with them between the two tests. After shooting the rifles on a warm but calm afternoon, and carefully measuring and recording the target results, I put them inside well-padded soft cases so the scopes won't get bumped, then place the cases someplace safe.

When a cold night comes along I move the cased rifles and ammo into my unheated garage overnight, then leave them in the cases while transporting them to the same range, and at the range keep the rifles in a standing rack so they'll stay cold.

The tests are always made at the same range, with the same rests, over the same chronograph. In contrast to the rifles and ammo, the chronograph is kept warm, first inside my house before heading to the range, and then inside the cab of my warmed-up pickup. I also make sure the working parts and batteries of the chronograph stay warm, with different methods.

During the tests I often fire ammo loaded with different powders but the same bullet, but also test loads with different bullets, and don't fire quickly enough for the barrel to warm up significantly. Partly this is because the heat waves from even a slightly warm barrel interfere with aiming correctly through a scope on a very cold, calm day. If a barrel starts to get that warm I put the rifle in the rack, action open. They cool off very quickly at zero.

Have been doing this since 1991, and so far every handload that resulted in the same basic velocity at zero as at 70 has also shot to the same place at 100 yards, with similar accuracy. Only those that differed significantly in velocity have shifted point of impact measurably at 100 yards.

"Significantly" is defined as more than 25 fps. The same loads will often average 25 fps from string to string anyway, even when chronographed within the same hour. Only once has a load chronographed exactly the same at zero as at 70, which was pure chance, but a lot of loads with certain powders have differed less than 25 fps.

Cartridges loaded Hodgdon Extremes normally chronograph within 15 fps of their warm-test temperature, and so far have never shifted point of impact significantly at 100 yards, in a number of rifles. Cartridges loaded with Ramshot TAC and Big Game have also done very well, and a few other powders in certain applications. IMR4895 and IMR4350 have proven pretty cold-resistant in my .375 H&H with 260 and 300-grain bullets, only losing around 30-40 fps, but IMR4350 lost around 75 fps in the .30-06 with 165's.

It's not unusual for other powders to lose over 100 fps in the same temperature range, and the most I've seen is 184 fps. Sometimes the point of impact at 100 yards doesn't change, but often it does. As I've noted before, it seems to depend on whether POI also differs significantly when working up handloads with different powder charges. It also seems to be related to barrel weight. Varmint rifles with heavy barrels don't usually change POI much, if at all, which is similar to how they act when working up loads. Big game rifles with light barrels are usually the problem.

However, one of my favorite temperature-test rifles is my NULA .30-06 with a #2 Douglas, which doesn't change POI much when working up loads, probably because of the full-length barrel bedding in a very stiff synthetic stock. It's also very accurate, so any change is easily measurable. But the one load that lost 184 fps still changed POI noticeably, shifting 1.5 inches left and two inches down at 100 yards, while the rifle's primary load (using H4350) didn't shift POI at all during the same test.

So no, I don't believe the POI changes were due to scopes or mounts shifting, or walnut stocks warping.

Thanks for sharing that. I have done similar tests and like I stated, anything but a straight down drop I always blamed on something else. Now you have me wondering.

I have used IMR 4350 extensively in the cold. Mostly in 30-06 with 165s and 7mm-08 with 140 Partitions. These are 2 I used to use a lot back in the day. Both would normally shoot a bit lower in sub-freezing temps.

I would say H4350 may be the least temp. sensitive of any powder, even beating Varget, which is very good.

I have been loading R-15 in my 7-08 for maybe 5-6 years now. I sight in during November temps. I remember you saying that they changed R-15 and it may be less temp. sensitive now, or something to that effect. I am wondering if my powder was mfg. before or after said change. Any way of knowing? I guess I could call them. I have the better part of a 5 pounder of R-15 left.....

John, since H4350 is rarely available in my area now I have been researching alternatives for 120g-140g Swede.

Do you have similar temp info on other powders like R19, R23, maybe IMR 4451 that would work + are available? I had temp issues with R22 but I don’t hear much about R19 temp issues, and I have read that 19 works well for you in your swede.

Thanks,
Tim

It's the same reason POI can shift horizontally when working up loads. If the cold is enough to affect the velocity very much, then it has effectively mapped it onto what would be a different load at normal temperature. The load pings the barrel differently for lack of a better description.

That is kinda what I was thinking. I used to do all kinds of testing and such. It has been a while now. I really haven't noticed much in regards to sideways shifts in POI in rifles I use in cold temps a lot. Any changes usually involve similar groups, just lower on the target.

Except for the big bore handguns, which incorporate large chunks of frozen steel, and sometimes steel mounts, and powder that I know is temp sensitive........

stealthgoat,

RL-19 does work well in my 6.5x55--at "normal" temperatures. It's not very cold-resistant so I don't hunt with it much here in Montana.

I've been switching all my H4350 loads to IMR4451, which has been very easy. So far the Enduron powders have been very good at various temperatures.

Just started working with RL-23 this summer and have a great load worked up for my Tikka .260, but won't know how well it works in cold until I run some more tests this fall. Alliant claims it's great.

2muchgun,

The change in Reloder 15 took place around 2000, so your powder should be the more resistant version. The old stuff was pretty sad, but the improved RL-15 is pretty good. One of my primary RL-15 uses is 200-grain bullets in the .338 Winchester Magnum; in my 70/zero test the load lost 36 fps and POI at 100 yards was unchanged.