Home Forums Hunting & Shooting Ask The Gunwriters The American Rifleman has a newer Field Editor

The NRA's American Rifleman gained considerably with it's newer Field Editor.

He wrote a pretty in depth and interesting article about
Hot & Cold, Temperature's Effects On Ammunition.

I do have one question about the article.

In it, the writer states,

"I recently tested a 257 Wby. Mag load using Ramshot Magnum and the 100 gr. Barnes Triple Shock X bullet in a Weatherby-Vanguard Sporter.
At 70 degrees F this load grouped three shots into a half-minute of angle out to 400 yds. with a muzzle velocity of right around 3500 f.p.s. AT zero degrees it lost about 150 f.p.s. or about 4 percent of its warm weather velocity, but point of impact and accuracy remained virtually unchanged.

Even at 400 yards you did not have POI change?
That's amazing after losing 150 fps.

What is the most temp sensitive powder you have ever used?

That is amazing.

Well, he did say "virtually unchanged." Which doesn't mean NO change, it means the change was inconsequental.

I haven't done any sub-freezing shooting, so can't say from experience. So unless there's some sort of typographical error, I must believe him. I don't think he'd print something that isn't true, no reason to do so.

I remember reading in a loading manual that 200 fps change in a 30-06 (IIRC) made a tenth of an inch difference at 100 yards. Extrapolate that (if it's true) to 400 yards, it's still virtually "unchanged" unless you're shooting from a machine. In other words, natural error wouldn't allow you to tell a POI change.

I didn't shoot in cold weather at 400 yards, just at 100--where the POI was unchanged.

I realize the quote makes it sound as if maybe I shot at 400 yards in the cold test. I can't remember right off if I wrote it that way, or if that's how it got edited.

A quick look at a ballistic table indicates that a loss of 200 fps with that load would have the bullet landing about 2 inches lower at 400 yards.

By the way, I have been listed as a Field Editor for AR since this past winter. The hot-and-cold article was my 4th to be published since then, I believe.

I have seen some rifle powders lose 15% of their velocity when shot at zero F as compared to when the same loads were shot at 70. I've also seen some that often resulted in definite hang-fires, as noted in the article.

I'd hate to pick out any powder as the most cold-sensitive, because how much velcoity they lose also depends on the cartridge, primer, etc.

out to is not the same as at...

Great article, and on a subject that isn't often written about. BTW, this issues of American Rifleman was probably the best issue I've seen in years: Barsness, Selby, a long look at double rifles. Can't get much better.

Mule Deer, didn't know it was you he was talking about.
Looks like you're cropping up everywhere!

Somehow I knew that but could not remember when. I should have stated newer. Anyways JB thanks for the article I enjoyed it.

JB is the only gunwriter I can remember other than Hagel who has written on the issue of temperature sensitivity of rifle powders.

Bob Hagel inspired my experiments, but I must admit that I found his methods a little lacking. For one thing, heating or cooling the ammunition is not the whole story, and that's all he did, then shooting the ammo in a rifle at normal temperatures.

To simulate hunting conditions, the rifle also has to be warm or cold. Otherwise a 70-degree rifle tends to warm up the ammo in the chamber, especially the primer, a big part of the deal.

Hagel also didn't report on point-of-impact changes, another essential part of the equation.

It is a big PITA to shoot at zero F., and a little bit of a PITA to shoot at 95 (about as warm as it gets in my part of Montana) but it's the only way to find out what will actually happen.

Shooting a 5 shot string in the 6.5x284 the first 3 shots were
within 20 fps of each other the next two went completely wacko on me.

Does shooting heat up the barrel chamber for the following shots?

What do you mean by "especially the primer"?

JB: Yes, I remember that he shot from an enclosed room and cooled the ammo IIRC.Only in a passing manner did he mention POI changes.

I shoot all winter myself,and it is a pain to shoot at 10 degrees;it does not frequently get to zero where I live,but I remember shooting New Years Day this year and it was COLD!

I can't say that I conducted experiments, but did notice that certain powders lost velocity.Among the standouts(in lost velocity) have been 760(in the 375H&H),IMR 4350,and IMR4831.

Curious thing about IMR 4831 is that it did far better in the 270 than it did in the 7RM,leading me to the "probably erroneous theory" that some of this temp sensitivity may be related to the amount of air-space in the case,and how the powder bulks in the case,ie.what % of space the powder occupies.I dunno....

SU-try this sometime, and remember it's coming from the loonie bin...grin

When I am shooting for accuracy many times I'll use the probe thermometer that I have in my shooting kit to take barrel temps.

This isn't perfecto I know but here's what I do.

B4 I shoot the gun I stand it up in the gun rack and stick the probe therm (one that restaurants use) in the mzl end. That'll give me an interntal temp of the tube when it's cool and unfired.

Then after my string I'll stand the gun back in the rack and stick the therm in the barrel again. Then I'll not shoot another string until the barrel goes back down the original temp that it was at when I first took its temp.

A bit loonie I know but when I am really working on accuracy (specially at long range) I try to do it. It works pretty darn well for me, unless I'm just feeling impatient that day.

Best of luck to ya!

Dober

(SU, you gonna do any fall bruin hunting?)

Just in passing - a bit off, but somewhat relevant - I have taken to blowing a puff of air down the barrel after each shot. It is amazing how much smoke comes out from some powders. It really seems to take a fair amount of heat out with it as well. We generally shoot two three shot groups before alternating shooters/guns. Sometimes we have a fan set up to blow air down the resting gun and sometimes we lay a wet rag over the barrel from chamber to muzzle.

SU35,

Yeah, the chamber gets hot after a few shots, how hot depending on the rifle, chambering and (especially) ambient temperature. In fact while prairie dog shooting on 90-100+ degree days we have occasionally "cooked off" chambered rounds without every pulling the trigger. This generally happens when the shooting is fast and furious and we forget to switch rifles now and then to let a hot one cool down.

The primer cup is very thin metal and sitting right next to the bolt face. A warm bolt face will warm-up a cold primer quickly, and a warmer primer tends to light the powder better than a cold one.

Another little help is to quickly get the brass out of the chamber after firing.

John,
I hope people realise you're providing information that mostly is beyond what other than a very few hunters will ever experience. When a hunter selects an opportunity to take the shot, no matter what he is hunting, how many shots will go beyond 100-200 yards? I have killed game in temperatures near freezing and way, way over, the ton and also used the most horrible unmarketable powders available for temperature instability, but I never lost a single animals or recall a miss that could not be attributed to my holding stance.

Fellas, the point is, John is doing a lot of work to help you gain confidence in your gear and your skill to take those shots and not get excessively technical about it all. Enjoy your hunt and don't interfere with your hunt by worrying about powder stability.

Remember when it was fun?

JW

There is an article in one of the Cartridges of the World (I think #10, but I could be wrong) on frontal ignition. While it is completely wrong about duplex loading in the OKH, it is still an interesting article. One of the author's findings was how hot the cartidge cases were compared to those fired from normal cases, leading to the assumption that less heat was transferred to the barrel as well.

John,

I would disgree somewhat with your assessment. Point of impact can shift considerably at 100 yards in really cold weather (not just freezing), and not only up or down but in any direction.

One of my early experiments found a .270 load that shifted 3" to the right at 0 F., with the rifle sighted-in at 70. That would result in a shot 6" off at 200 yards, easily the difference between a lung-shot deer and one with a bullet right through its middle.

Then there is the difference than cold air can make on trajectory at 300+ yards. Yes, most hunting takes place at closer ranges, but in my part of the West 300-yard shots are quite common, and 400+ yard shots not rare. I have personally shot big game at temperatures down to 30+ below zero F., as have most of my friends here in Montana.

Hunting in temperatures around or below zero isn't uncommon in a lot of North America. The upper Midwest, New England, the Rockies anywhere from New Mexico north, Alaska all commonly experience such temperatures during big game seasons. And in the Rockies, central Canada and interior Alaska it's common to shoot at 300+ yards in zuch cold weather, because that's often when game is most active, even in open country.

I appreciate the amount of hunting you've done, but the northern half of North America is very different from Australia.

As a kid, one of my first caribou was shot at ridiculously close range in ridiculously cold weather, <-50F. I literally froze a toe that day in Bunny Boots.

The rifle was a 760 in 35Whelen and the shot was a hang-fire. If the caribou had not spotted me and stood staring until the shot went off there is no doubt I would have missed... As it was the Speer 225 remained mostly unchanged after going through the chest and stopping along the ribs, down low in the cavity.

I have no idea where the rifle was actually pointing by the time it went off.
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