Hi guys from my reasoning, a single base powder should be more temperature sensitive than a double base powder.
However as far as I can theorise in my mind, double base powders that contain nitroglycerine (dynamite) and nitrocellulose as opposed to single base powders that contain only nitrocellulose.
All powders have coatings which modify the burn rate. According to the book “Ammunition Making” by Frost, this deterrent coating is typically di-butylphthalate. This is not a simple question, because I have not found a simple answer. If you have access to the book, I recommend reading the chapter on Powder. What is true is that temperature greatly increases combustion pressures.
It is hard to believe but even the Army has forgotten this. Around 2010 the Army was first article testing SAWS and put the rifles and ammunition into thermal chambers at 160 F. The end result were weapon malfunctions. The average pressure of the 5.56 round is 52,000 CUP, but the Army calculated at 160 F, the average pressures were closer to 80,000 psia! What the heck they thought they would prove, or find out, by sticking ammunition in an oven is beyond me, because the phenomena of heat producing high pressures should have been well known. Apparently this is not well known in the organization and the reason has to be a massive loss of technical core competency. If you search DTIC, what you find is that the Army performed a cover up; claimed oil was the problem, issued warnings about oil on cartridges. Hot ammunition was, ignored, as a cause of the malfunctions.
Would be more susceptible to extreme pressure spiking on the upper end with and likewise more likely to have low end detonation problems (though I am not 100% convinced on the theory of these) with charges that are too light.
Since the whole event is an exponential curve, it does take much to shift the curve or modify the slope, and that would be relatively independent of the composition. Nitroglycerine is added to the nitrocellulose to provide more energy, but I don’t think that makes double base any more “peaky” within the pressure ranges we encounter in small arms. Double base would probably make a better explosive in a HE shell, as it has more energy per grain, but we are not trying to blow our guns up.
While Im not a propellant chemist, I have see a few things. First the only powder that Ive had decompose has been a single base powder
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That is luck of the draw.
I still have some DB powders That go back into the early '60s. Most of the old stuff was out in the old leaky, drafty toolshed back where I grew up. Temps from -10 up to 100.(Temperate climate). The general consensus Iv heard over the years is that the DB powders are more stable over time and are fairly tolerant of conditions. SB are more likely to break down if not kept under stable storage.
I was listening to Car Talk this weekend, Click and Clack agreed with a letter that stated that two people can be more ignorant than one. The two people in question were of course, Click and Clack. I think the phenomena is basically true and can be proven. The more teenagers you put in a car, the overall intelligence within the vehicle goes down by the inverse square of the individuals. Two teenagers are four times as stupid as one, 4 teenagers are sixteen times stupider than one. We have all seen this.
The general consensus is wrong. The rule of thumb for gunpowders is that single based powders have a shelf life of 45 years, double based 20 years. Given that production conditions, storage conditions, vary so much, lifetime of powders vary considerably in the real world. But, the reason double based powders have a shorter lifetime is because nitroglycerine attacks the double bonds on nitrocellulose and breaks down the powder grain. Over long term storage, moisture in the air will wick nitroglycerine to the surface, as the water ions condense and evaporate onto the powder surface, which makes the surface area of old double based powders nitroglycerine rich. This will spike combustion pressures.
Old single based powders will also blow up guns, because nitrocellulose is breaking down quite nicely, without nitroglycerine being present, and that causes burn rate instability.
The worst enemy of gunpowder is temperature, heat breaks down gunpowder at an exponential rate.
Also, SB powders usually exhibit a linear relationship between charge wgt and pressure, while the double base powders, especially sphericals operate in a narrow range of pressure and can "spike" when used out of these restraints. The only weapon Ive damaged over50+ years of hand loading including some wildcats was a beautiful K-38 that succumbed to Bluedot, a DB.
The pressure curve for single based and double based are both exponential curves. However, talking with Alliant, some combinations of cases, primers, powders, bullets, are unstable combinations. I called up Alliant and asked about Blue Dot and 223 loads. I know a number of shooters using Blue Dot in the 223. Low charges, shoots great, hardly any cleanup. Alliant told me that small changes in components with this combination would radically shift the pressure curve resulting in extreme pressures . This explains a number of blowups that are posted on the web, shooters using reduced charges of Blue Dot in rifle cases. For this reason, it is best to use only those powder/case combinations that powder companies recommend, as it is likely that the unpublished combinations showed a high sensitivity to component changes on their pressure guns.
I cannot explain your K-38 blowup with Blue Dot, but in my testing with Blue Dot in 38 Special, the extreme spreads are two to three times what I get with Bullseye, and I think that indicates, more than anything else, that this powder is not appropriate for this cartridge. Especially my note that the retort varied in intensity, with the same load, that tells me that pressures are varying a bunch.
Code:
[SIZE="3"]4" S&W M10-5
148 LWC 2.7grs Bullseye W/W cases WSP
19-Apr-09 T ≈ 60-65 ° F
Ave Vel = 696.2
Std Dev = 12.04
ES = 48
High = 721.3
Low = 673.3
N = 32
v accurate, about 2" low, no leading, mild recoil
125 gr LBBRNFP 4.5 grs Bullseye Mixed cases WSP
9-Apr-06 T = 64 °F
Ave Vel = 945.6
Std Dev = 27.28
ES = 75.21
High = 995.2
Low = 920
N = 6
125 gr LBBRNFP 6.5 grs Blue Dot Mixed cases WSP
9-Apr-06 T = 64 °F
Ave Vel = 734
Std Dev = 63.53
ES = 260
High = 829.6
Low = 569.5
N = 18
125 gr LBBRNFP 7.0 grs Blue Dot Mixed cases WSP
9-Apr-06 T = 64 °F
Ave Vel = 788.2
Std Dev = 63.3
ES = 241.3
High = 926.7
Low = 685.3
N = 12
125 gr LBBRNFP 7.5 grs Blue Dot Mixed cases WSP
22-Apr-06 T = 68 °F
Ave Vel = 867.3
Std Dev = 53.06
ES = 235.6
High = 959.7
Low = 724.1
N = 25
125 gr LBBRNFP 8.0 grs Blue Dot Mixed cases WSP
22-Apr-06 T = 68 °F
Ave Vel = 990.2
Std Dev = 56.55
ES = 236.1
High = 1093
Low = 857.5
N = 25
Elevation all over the place
very poor accuracy, loud at times
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