Home Forums Hunting & Shooting Ask The Gunwriters .338 WM cold temp powders?

This little fella took a 210 Partition over a bunch of RL19 right at 400 yards. Not saying it isn’t a problem but developing the load in 50 degree’ish temps and sacking the bull in 20’ish temps didn’t seem to matter much. My 338 has been pretty great with RL19 over the years and upon chrono work back home at nearly the same temps lost about 50 FPS, but that was back before the Magnetospeed as well.

I know temp sensitive matters at extreme range but for me, so far I haven’t had a problem.

I'm using r19 exclusively and shoot in temps between -20 or -30 to 75-80f. Not exaggerating...i shoot year round. I also use non-magnum primers as I find them more accurate. No issues here with grouping...though I don't chronograph each string.

My workup was in 60ish temps but I've not had pressure issues in hot weather nor ignition or group shifting in the bitter cold.

Keep in mind gents im talking punching paper at 100m

beretz,

50's to 20's usually doesn't result in more than 25 fps difference with any modern powder. In fact, usually 70's to 20's doesn't.

The critical temperature is around zero and below. This still MAY not make any difference at 400 yards, even if the velocity loss is 100+ fps, as long as the POI remains the same at 100 yards, as mathman pointed out.

Have tested many loads at 70 and zero. Usually there's no difference in 100-yard POI, even if the muzzle velocity's a lot slower at zero--but sometimes there is. I've seen as much as a 3" shift at 100, and it can be in any direction. That's unusual, but 2" is common with powders that lose considerable velocity in cold.

A lot depends on the rifle. Slimmer barrels usually show more POI shift, just as they do when working up loads, though sometimes they don't. But you never know unless you test 'em.

One thing I can say is that in 25 years of doing 70/zero tests with the same rifle and load, I've yet to see a significant difference in 100-yard POI with any load that varies 30 fps or less at those temperatures. And I've yet to chronograph any loads using Hodgdon Extremes that varied that much, regardless of the cartridge and bullet weight.

Many powders will do pretty well in certain cartridge/bullet combinations, but not other combinations. But again, you never know until you test 'em.

There's an article coming up on this in HANDLOADER that contains far more details, including a bunch of chronograph results for cartridges from the .17 Hornet to .375 H&H.

It's not something "wonky" with the rifle, but it is a combination of both velocity loss and the rifle.

Anybody who's worked up handloads should have observed that various powder charges, even with the same powder and bullet, do not always shoot to the same point of impact at 100 yards. This tendency is greater in lighter-contour barrels, especially when free-floated, but can occur even in heavy barrels, though the differences in POI won't be as large. This is because different powder charges change the vibrations of the barrel slightly--which is also why we try different powder charges, to find the charge that results in the smallest groups.

What I've noticed over the past 25 years of testing the same handloads at 70 and then again at zero is that rifles which show a noticeable (say an inch or more) POI shift at zero degrees are normally the same rifles that show larger differences in POI when trying handloads with different powder charges. In other words, if when trying various 165-grain loads with your .30-06, ammo with powder charges of 55, 56 and 57 grains of IMR4350 land in noticeably different places on the target, then that rifle is also likely to shoot the SAME load of IMR4350 to different places at 70 and zero degrees. While IMR4350 isn't as temperature-sensitive as some other powders, it does tend to lose velocity from 70 to zero degrees.

Exactly how much depends on the specific cartridge and load, but I've seen IMR4350 lose anything up to 75 fps from 70 to zero. This may not seem like much, but in that instance POI at 100 yards changed two inches--and upward. Loss of velocity does NOT always mean a lower POI at 100 yards, any more than higher velocity always causes a rise in POI when working up handloads. It all depends on barrel vibrations. (Have also seen IMR4350 lose only 35 fps from 70 to zero, in a different cartridge, with no change in 100-yard POI. As I've noted before, much depends on the specific load and rifle.)

Other odd things can happen. One of the very first cold-temperature tests I made was with a very accurate .270 Winchester, using both the original military-surplus H4831, and Reloder 22, then a relatively new powder. Like many .270's, this one tended to put 130 and 150-grain loads into the same place at 100 yards, and the most accurate 130-grain load used H4831, and the most accurate 150-grain RL-22. But something weird happened while hunting in very cold weather with the 150-grain load, so afterward I tested it on a cold morning, also trying the 130-grain load as long as I was out there.

Both loads lost well over 100 fps, the H4831 load 151 fps and the RL-22 load 129 fps. (Remember, this was the original WWII era H4831, not today's Extreme H4831, a totally different powder.) The RL-22/150 load shifted its POI 3 inches to the right, the reason for the weird result while out hunting. (I probably don't need to remind anybody of this, but a 3-inch change in POI at 100 results in a 6-inch change at 200 and 9-inch change at 300--NOT 3 inches at all ranges.) The 130/H4831 load did NOT change POI, but went from 3-shot accuracy under 3/4" at 70 degrees to nearly 2-inch groups at zero.

As I noted earlier in this thread, there's a long article on this subject about to appear in HANDLOADER. No doubt many people won't read it, because they don't want to pay money for information when there's so much free information on the Internet, especially from notable Campfire members like Savage 99, but also because their attentions spans are too short.

But perhaps the two major points in the article are that I've yet to see any noticeable change in POI at 100 yards with powders that don't vary more than 30 fps in velocity from 70 to zero, and that with powders that aren't temp-resistant, you never know until you test 'em at widely different temperatures. More often than not there isn't any difference in 100-yard POI, but when there is it can be significant.