Has anybody had problems with WMR powder? Last year I worked up a load for my .300 mag. at high temperatures. (100 to 110 degrees) with the intention of fine tuning it when things cooled down. When temps were in the lower 80's, I went out with the original loads that I'd saved for the starting point, and started to shoot. After two rounds I quit. Pressure seemed to be way out of line. Shiny ejector marks, stiff bolt opening, loose primer pockets.
Went home and broke down ten rounds and check weighed the powder charges. They were right on the money. Neck sized the brass, recharged the loads, weighing each charge on two seperate scales (One electronic and one balance beam) Back at the range, blown primers, sticking bolt, the works. This load was safe with no problems at 110 degrees, but at 82 degrees blooey. I'm lost here. anyone have any ideas, or should I just burn up 15 pounds of WMR as a 4th of July fireworks deal next year.
Paul B.

It seems nobody else has a clue, and I don't either. I have heard people talk of the possibility of powders with negative temperature coefficients, but I have never seen one.

It sure sounds like you found one.

Seeing all the care you took with the rounds, I don't think it likely, but I have to ask -- is there any chance your barrel is heavily copper fouled?

Stumped in Cincinnati,
Don

Do you suppose it is possible the primers were hotter (more forceful) on the 110 degree day?

I know this will sound insane to you guys, but I'll give it a whirl anyway as it is the only idea I have.

Lets assume the primer fire and pressure, was hotter on the 110 degree day. As the primer ignites, the immediate primer pressure pushes the bullet forward as the powder begins to combust. The powder burned and all was well.

On the cooler day, the primer was less energetic and pushed the bullet forward less than it did on the hot day.

The insane theory is: we now have a higher load density because because the primer didn't push the bullet as far forward before the powders combustion, hence higher pressures.

[This message has been edited by Scott H (edited 08-11-2001).]

Don G. No. The barrel was not heavily fouled with copper. Sometimes I am almost anal about copper fouling, so no, there was very little if any.

Scott. Interesting theory. You never can tell. However, I got a post on another forum from someone in the shooting trade that said that Winchester discontinued W-785 because of temperature sensitivity and replaced it with WMR. Seems like, according to this "insider", that WMR has been shoen to have the same problems. BUMMER! I'm stuck with almost 15 pounds of the stuff. (Got a good deal, I thought.) Too bad. The first tests looked like it had a lot of promise.
Paul B.

Paul I have used W785 and the newer WMR and found them to be sensitive to temp variations but not the way you have experienced. I have found that the max load in cold weather would be several grains higher than the warm weather max. That would then make the cold weather load excessive in warm weather.The only thing I can suggest that may account for what you have experienced is you may have carried the loaded ammo around in a vehicle for a while and the vibration has worn some of the deterent coating off of the powder.This make the powder burn much faster and increase your pressure.

Paul,
What were your chronograph readings? If presure was too high, velocities would also be higher. Or, put another way, a smaller charge should produce higher velocities under the cooler conditions. Since hunting mostly takes place in cooler conditions, your powder is OK, you must reduce load a bit.

I have used WMR in 270 loads and it was fine. I saw someone bemoaning the fact that they had discontinued the powder without letting them know, and was looking for some. I suspect you can move your WMR if you find you cannot use it in your load.

By the way, I had the same thing happen to me recently with H4831. Developed loads at 95-100 degrees. Took them to Africa where it was much cooler (50-60 degree cooler), and had pressure problems. No one could offer an explanation for this either.

Ku-dude

[This message has been edited by ku-dude (edited 08-13-2001).]

This really seems like a stretch, but is there any chance that the barrel shrunk more than the bullets as the temperature dropped?

What type of bullets were you using?

Don

Out of curiosity, were these heavily compressed loads?
C.G.B.

A powder is not only sensitive to temperatures, it�s also sensitive to how much moisture it contains. Same powder stored in an open cup for some length of time can can act very different depending on how much moisture it has gained or lost. A loaded round is not so sensitive, but I would not be surprised if a hotstored round, maybe real hot from sunheat could dry so much that an already hot load becomes too hot.
It is airspace even in a full case, and hot air can take up more water from powder than cold air. It may also be easier for that air to leak out via primerpocket in hot conditions than leak back in cold conditions. An already compressed load should make that difference bigger.
Goran

Gentlemen, I thank you for your responses, and I'll try to address them all.

Snowman: The ammo was loaded the night before and taken to the range the next day.
Brass was from a lot of 200 rounds purchsed about a week before.

Ku-Dude:Chronograph reading averaged 3070 FPS. My rifle has a 26 inch barrel, and Winchester factory ammo produces 3050 FPS, so I don't think I'm too far off there.
I have also worked up a nice .270 load for my Ruger #1 with the 150 gr. Sierra. I haven't chronied it yet or tried it in cooler weather. (It ain't cooled off here in months. )

Don G. I agree, it really is a stretch, but at this rate, I'm about ready to believe anything when it comes to this load.
The bullets were the 180 gr. Sierra spitzer flat base.

CGB. No, the load was about a 95 percent case full. No compression at all that I could tell.

Goran. I am under the impression that double based powders, and especially Winchester's ball powders are not that sensitive to atmospheric moisture. In fact, an incident thast occurred a few years back convinces me that this is probably rather factual.
I bought a can of IMR-4350 and acan of W-760 with plans to work up some loads in a 7X57. Somehow, I got sidetracked and the powder cans were left out in my shed, and as stuff got moved around, the cans buried and forgotten. About five years later, while clearing out a ton of juck from my shed, I came across the two cans of powder. Well, the 4350 was a total loss, completely deteriorates to a red dusty fouls smelling mess. The W-760? I tried some in my pet load for the .308, and it shot fine, no apparent changes in pressure and velocity was in the ball park. I even have some H-335 that has to be at least 25 years old. Still looks good, although I haven't tried it.
FWIW. My powders are stored in an air condiioned area, but I do my handloading in my shed. After 23 years, I finally put an A/C unit in there. Loading ammo in a shed in the Arizona summer ain't much fun.

I've been handloading ammo since I was 16 years old. I'm 63 now. This is the first time I've run into this, and it sure has me scratching my head.
I have gooten a reply from Sierra Bullets on this, and all they said was WMR has a temperature sensitivity problem. Winchester never has answered my question.
Guess I can try a grain or two less, or use it in something else. With 15 pounds of the stuff, I could make a nice fireworks display come Independance Day.
Paul B.