I'm not as educated about powders as some here, but it has long been my impression that old degraded powder actually produces lower pressures. This may very well be incorrect, so I'm going to follow this thread with an open mind.
The source of this horribly incorrect information are "in print" gunwriters. Gunwriters are not required to have or pass any minimum professional standards. Real professions, such as Medical personnal, Engineers, etc, are required to take a certain number of courses at accredited institutions, perform internships, etc, before they are considered as qualified in their professions. The very best gunwriters were Journalist Professors, French majors, or guys who simply carried a gun on their hip. Well, anyone can wear a belt. Gunwriters don't have to have any education, training, or intelligence because their job is primarily advertizing. As long as their infomercials are interesting, and they accurately repeat what they are told by Corporate Advertizing bureaus, they are considered fully qualified in their job. The end result is that these guys don't have the background, and in many instances, intelligence, to sort through myths and legends. As a consequence they are highly susceptible to self serving corporate psuedo science and to accepting falsehoods as truths. And this one, that gunpowder fails safe and benign, is another gunwriter whopper that is totally wrong and false.
The bottom line is that nitrocellulose is a high energy molecule that is breaking down to become a low energy molecule. Anyone who has taken thermodynamics will realize that this is obvious, everything is breaking down to a lower energy state, but somehow, shooters have been lulled by gunwriters into thinking that the second law of thermodynamics does not apply to our sport.
The first thing you will notice with old gunpowder is a loss of performance. I have chronographed old LC Match 30-06 and the extreme spreads were much higher than new ammunition. At the very end of its lifetime, old gunpowder creates a safety issue. The primary reason gunpowder becomes dangerous is deterioration of the powder grain. The powder grain was engineered to a constant shape and as powder deteriorates, that shape is altered unevenly. This creates “burn rate instability”. For all your cartridges you want a nice and smooth pressure curve. If the burn rate is irregular, because the nitrocellulose powder grain is irregular, instead of a smooth pressure curve there will be irregular pressure curve. These irregularities can interact in such a way that pressures spike. Double based powders are a combination of nitroglycerine (NG) and nitrocellulose, the NG is there for an energy boost, but unfortunately NG causes a new set of problems. NG is not bound to the powder grain but is a liquid and it migrates. Water condensing and evaporating on the powder grain surface wicks NG to the surface of the powder grain over time. This creates a NG rich surface. So, even though the total energy of the grain has decreased due to breakdown, the surface is NG rich and that will spike the initial burn rate. Another thing NG does is accelerate the breakdown of the base nitrocellulose molecule by attacking the double bonds holding the NO molecules. So double based powders have less than half the shelf life of single based (nitrocellulose only) gunpowder. Unfortunately all ionic compounds attack those double bonds, water is a main offender because it is always in air, is a polar covalent ion (acts like an ionic compound) and thus you know the reason you were told to store gunpowder in a cold and dry environment. Incidentally rust is bad and that rust that came out of those old tin cans accelerated the aging of gunpowder, and I think, is why they went to plastic containers.
Gun powder physically breaks down and that red dust you see in old powder cans is finely grained gunpowder. The surface area of that dust is huge. People just don't know the explosive effects of dust, but just google coal dust explosions, cotton dust explosions, wood dust explosions. When carbon based compounds break down into fine dust the potential for an enormous explosion is high and the history of dust explosions is vast. Gunpowder dust will spike the pressure curve and there are a number of blown up guns after which, the gunpowder in pulled ammunition was found to have decayed to a dust.
There is almost no data on the internet because all that was ever needed to be known about gunpowder aging was determined well before WW2. However ball powders did come out at the end of WW2 and I was able to find this data showing that gunpowder at the end of its lifetime will pressure spike. Heat is used to accelerate the age of gunpowder, so what you are seeing is in fact because of “age”, not heat, but it took heat to age the powder quickly. The IMR is a single based and the WC is a double based ball powder.
INVESTIGATION OF THE BALLISTIC AND CHEMICAL STABILITY OF 7.62MM AMMUNITION LOADED WITH BALL AND IMR PROPELLANT
Frankfort Arsenal 1962
3. Effects of Accelerated Storage Propellant and Primer Performance
To determine the effect of accelerated isothermal storage upon propellant and primer performance, sixty cartridges from each of lots E (WC 846) and G (R 1475) were removed from 150F storage after 26 and 42 weeks, respectively. The bullets were then removed from half the cartridges of each lot and from an equal number of each lot previously stored at 70F. The propellants were then interchanged, the bullets re-inserted, and the cases recrimped. Thus, four variations of stored components were obtained with each lot.
Chamber pressures yielded by ammunition incorporating these four variations were as follows. These values represent averages of 20 firings.
Heat is the worst enemy of gunpowder. Heat accelerates the breakdown of gunpowders, and it is an exponential function.
Surveillance and in-service proof - the United Nations
http://www.un.org/disarmament/conva...20-Surveillance_and_In-Service Proof(V.1).pdf
After reading this thread, I pulled pulled several rounds of 7 mag dated 7/1I/ 2001. Now I know this is 20 yr. old ammo, but still, 14 years is certainly not fresh ammo in this regard. These were loaded with RL22. The powder smelled great, no red dust, and it wasn't clumped up. The only thing I noticed was that the bullets had developed a serious welding to the necks. I tried pulling the first one straight out with the collet puller, it took a lot of compression on the collet just to hold onto to it, and some extreme force to break it free. I used the seating die to break the weld on the other 2 rounds, and when I pulled them they slid right out nicely.
I have a box of factory Federal 7 mag my son had picked up at a yard sale, this box is really old, like 1993 if I recall. I shot a couple rounds at the range a few months back, the pressures were through the roof, bolt was locked up tight, primers flow was completely flush with the case head, so I quit shooting them. I took them home, pulled a couple to check the powder for break down, which wasn't apparent. So having checked the powder, I decided to just bump the rest to break the weld, which was an obvious condition, then I pulled them part way, then seated them back to the original oal. Last trip to the range I tried them again, and this time they were fine.
Thanks for sharing this. A bore obstruction is created when bullets weld to case necks. This can and has blown firearms as this changes the shape of the combustion pressure curve. The whole 1921 "Tin Can" ammunition fisaco was due to bullets welded to case necks. The Army plated bullets with a tin coating, to eliminate bullet fouling. The standard bullet jacket was cupro nickel and that fouled barrels terribly. Shooters were coating the bullets of the period with grease, as that prevented cupro nickle jacket fouling, but grease is messy and attracts dirt, so industry and the Army were looking for a better bullet jacket. Unfortunately for the Army, the tin jacket coating migrated into the brass case necks, a process called cold welding, and soldered the bullet to the case neck. This resulted in blown up rifles at the National Matches. This was incredibly embarrassing at the time due to the high visibility of the National Matches. Instead of fessing up and admitting that they had created unsafe ammunition, the Army lied, created a coverup and blamed greased bullets! Grease was banned from all Army matches and an extensive in print coverup was conducted for decades, by the very guys who made and issued the ammunition!.
I am of the opinion that your weld between bullet and case is due to corrosion caused by nitric acid gas which was outgassed from the powder.
