Primer temperature sensitive?
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troy fairweather
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i have seen tests, can't remember where. but have seen 308 puma small rifle brass loads not go off when hunting in cold weather. the primers went off but did not light the powder. same cartridge and powder and a large rife primer i never had any problems in the cold. .
Demi-human
maybe likes firearms a little bit…
Short answer: Yes.
Long answer: Yes, but it runs the whole system long... from whether your brain and body can sense it, to the effect the cold has on the firearm's ignition system, to the powder in the case as in Troy's example. All the way to temperature effects on the shockwave speed that propagates through the primer cake's compound.
A human can detect a cold weather hang-fire, the powder needing a higher pressure at cold temperature. As well as light striking pins not igniting the primer fully.
However, if the primer actually produces less heat and pressure when cold, or produces it at a slower rate, I don't know. If just the primer was cold and the rest of the system at room temperature, and the human at body temperature
, it would be very hard to tell...
Long answer: Yes, but it runs the whole system long... from whether your brain and body can sense it, to the effect the cold has on the firearm's ignition system, to the powder in the case as in Troy's example. All the way to temperature effects on the shockwave speed that propagates through the primer cake's compound.
A human can detect a cold weather hang-fire, the powder needing a higher pressure at cold temperature. As well as light striking pins not igniting the primer fully.
However, if the primer actually produces less heat and pressure when cold, or produces it at a slower rate, I don't know. If just the primer was cold and the rest of the system at room temperature, and the human at body temperature
, it would be very hard to tell...denton
Member
I did indeed test primer sensitivity. I'm away from my computer right now, but will post a full response in the next hour or two .
frankmako
Member
Yes it can, but I don't think you would be in a situation were the temperature swing would effect the primer and/or powder. A swing that bad would do more damage to you before the primers.
FROGO207
Member
Both the primer and the propellant are heat sensitive to some extent. I use magnum primers on some loads that do not call for them just to be sure the will fire in cold weather. My protocol is to work up loads in the warm weather and test them in the cold after I find a good one.
TRX
Member
Frost's "Ammunition Making" has a sizeable section about primer temperature sensitivity. He worked on priming compounds for Olin. He said there were a lot of perfectly good priming compounds, except they didn't work well when the temperature got much below freezing.
This has been the problem with "innovative" military ammunition; the DoD temperature requirements are where many of the fancy powders, priming compounds, and plastic case or caseless ammo has foundered.
The Soviets stayed with one of the oldest, and almost perfect priming compounds - plain old potassium chlorate. It worked anywhere from Anadyr to Afghanistan... and the Red Army didn't care that it was corrosive; cleaning guns kept soldiers out of trouble...
This has been the problem with "innovative" military ammunition; the DoD temperature requirements are where many of the fancy powders, priming compounds, and plastic case or caseless ammo has foundered.
The Soviets stayed with one of the oldest, and almost perfect priming compounds - plain old potassium chlorate. It worked anywhere from Anadyr to Afghanistan... and the Red Army didn't care that it was corrosive; cleaning guns kept soldiers out of trouble...
243winxb
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https://apps.dtic.mil/docs/citations/ADA488258
Now thats COLD -65 F
Page 20
Now thats COLD -65 F
Page 32 4.0 Summary and Conclusions.
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denton
Member
The common knowledge in this case turns out to be at odds with experimental results. Not trying to tread on toes here, but experiments contradict a lot of what we've been told.
For those less curious, here's the bottom line: Neither powder nor primer temperature is the likely culprit in temperature sensitivity in the range I tested (40F to 99F). If you want to know what happens when its REALLY cold, I don't have the answer.
A drop from 2750 to 2700 FPS for a 180 grain projectile is a drop of 108 ft-lbs of energy. That is only 35.4 calories, or enough energy to raise 454 grams of iron (about a pound) by just .7 degree C.
The rate of energy transfer between two bodies in contact is proportional to the difference in their temperatures.
The effect of temperature, as far as I could discover, is instantaneous. That rules out the temperature of the powder as being the main factor, since it requires a matter of minutes for powder temperature to equalize with ambient temperature or chamber temperature. You can separate powder temperature from firearm temperature and primer temperature if you're quick.
I ran a fancy statistical test that allows the testing of multiple variables at once, plus all of their interactions. One of the factors was primer temperature. The base of the test cartridges was squirted with circuit cooler and fired as quickly as possible, and well before the powder in the case could adjust. This separated primer temperature from powder temperature.
Findings:
Primer temperature doesn't matter, at least for the primers and temperatures I tested.
Barrel temperature near the chamber is by far the strongest variable affecting muzzle velocity change.
Ammunition temperature is about 1/3 as important as barrel temperature.
Given all the evidence, my conclusion was that the basic mechanism is that the barrel, the brass case, and the bullet rob heat energy out of the gas, and that cold metal robs more energy than hot metal.
In the experiment I ran, a temperature insensitive powder compensated for temperature by slightly adjusting its burn rate. Each powder is designed for a particular cartridge geometry, and works well in what it was designed for. H4350 matches the 30-06, and Varget matches the 308. But Varget is definitely not temperature stable in the 223.
For those less curious, here's the bottom line: Neither powder nor primer temperature is the likely culprit in temperature sensitivity in the range I tested (40F to 99F). If you want to know what happens when its REALLY cold, I don't have the answer.
A drop from 2750 to 2700 FPS for a 180 grain projectile is a drop of 108 ft-lbs of energy. That is only 35.4 calories, or enough energy to raise 454 grams of iron (about a pound) by just .7 degree C.
The rate of energy transfer between two bodies in contact is proportional to the difference in their temperatures.
The effect of temperature, as far as I could discover, is instantaneous. That rules out the temperature of the powder as being the main factor, since it requires a matter of minutes for powder temperature to equalize with ambient temperature or chamber temperature. You can separate powder temperature from firearm temperature and primer temperature if you're quick.
I ran a fancy statistical test that allows the testing of multiple variables at once, plus all of their interactions. One of the factors was primer temperature. The base of the test cartridges was squirted with circuit cooler and fired as quickly as possible, and well before the powder in the case could adjust. This separated primer temperature from powder temperature.
Findings:
Primer temperature doesn't matter, at least for the primers and temperatures I tested.
Barrel temperature near the chamber is by far the strongest variable affecting muzzle velocity change.
Ammunition temperature is about 1/3 as important as barrel temperature.
Given all the evidence, my conclusion was that the basic mechanism is that the barrel, the brass case, and the bullet rob heat energy out of the gas, and that cold metal robs more energy than hot metal.
In the experiment I ran, a temperature insensitive powder compensated for temperature by slightly adjusting its burn rate. Each powder is designed for a particular cartridge geometry, and works well in what it was designed for. H4350 matches the 30-06, and Varget matches the 308. But Varget is definitely not temperature stable in the 223.
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