Savvy_Jack said:
Would it not be the same with the Dupont No. 2 powder and Sharpshooter powder tests? Question is, if the velocity increases with "newer" powder, the pressures would also have to increase. Meaning that if the 1963 loads should create higher pressures/velocities, then all of the other old powders tested (pending deterioration) would also have to increase?
If the 1963 loads are decreasing in quality, would the 1960's and 1979 factory loads also possibly be effected?
What determines the kinetic energy in a bullet is the average pressure in the barrel during the bullet base's whole length of travel, from starting position in the case all the way to the muzzle. If you have a slower powder, it will allow you to put more energy in the case and it makes more gas, which means the pressure behind the bullet is higher past the peak pressure value than it is for a faster powder. When you include that greater post-peak pressure's bullet accelerating force, you find it can get to the same
average pressure, and thus the same kinetic energy and velocity with lower peak pressure than the fast powder can.
As far as the deterioration of powder goes, it is highly variable. The breakdown is caused by random molecular attempts to reach lower potential energy states triggered by randomly high points of heat concentration. This happens to both nitrocellulose and nitroglycerin. The breakdown produces nitric acid radicals. Left unchecked, these acid radicals help adjacent molecules to break down, causing a snowball effect that accelerates the overall breakdown of the rest of the powder around it. To prevent this, diethylamine or calcium carbonate are added to the powder formulation to act as a stabilizer by neutralizing the acid radicals. The exact amount of stabilizer varies by formulation and by lot, so how much powder has to break down before it is used up is variable. That means how weak the powder can get before it goes bad is variable. Because this is a heat-induced phenomenon, the lower the storage temperature of the powder, the lower the probability of random molecular vibration causing a heat concentration point that breaks a molecule and releases an acid radical. Powder kept in a freezer could well last centuries. Powder kept in a shipping container in an outdoor yard in Arizona could be bad in under two years.
So, no, you can't count on age in years to tell you the state of a particular lot of powder. The only generalization you can make is that it weakens with age until the stabilizer is consumed. After that, it either weakens rapidly and starts to corrode cases with acid radicals or, if the powder relies on deterrent coatings to keep its burn rate down, the acid radical can destroy some deterrents faster than the nitrocellulose or nitroglycerin, in which case the burn rate is radically increased. Board member Slamfire had some information posted about the Navy aging powder at, IIRC, 140°F for 18 months and having the peak pressure of 7.62 ammunition thus aged increase by about 150% (again, IIRC; from CUP's in the upper 40,000s range increased to the 70,000s range). There were some photos online of a Garand action destroyed by late 1940's production ball ammo that probably hadn't been stored well. On the other hand, a lot of folks have fired much older ammo than that without damage.
So, there is a big random element to the condition of aging powder. Unfortunately, the only way I can think of to determine what original lots produced is to contact their manufacturers to see if old records still exist to be mined for historical data. You can contact SAAMI to see how their standard for the 44-40 may have changed over the decades (if it has).
You might try contacting SAAMI to see if you can get permission to buy some current reference ammunition to calibrate your test barrel with. They don't normally allow non-manufacturers to obtain it. They used to but found the lots would tend to be exhausted too quickly and could come up short when a manufacturer needed them. However, since you have a site and do a lot of work devoted to this one cartridge, you might be able to ask them for an exception.