You know, there is no particular reason to assume they are not shootable. The primers may have dudded out, what was available at the time would have been the chlorate primers, which are corrosive, but not as corrosive as black powder. Blackpowder is chemically very stable and unlike smokeless powder of that era, as long as the charges are kept dry, the loads are as good as they are when the ammunition was reloaded.
It is probable that the cases are the balloon head type, which is an extremely weak case design.
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Solid head on left, balloon head on right
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I purchased some vintage used balloon head cases, and on sizing them, the case heads pulled off a number. I used lubrication and my old RCBS 45 LC sizing die. Luckily I used the vintage die because the decapping spindle must have been designed with this problem in mind. The spindle unscrewed from the top and I was able to get a brass punch in the die, place it on the rim of the separated case, and knock the case out. It would have been a real bear in solid top sizing dies. I would have had to hook the case mouth from the bottom. Based on that, I am leery of reloading my balloon head cases as I fear the case head blowing off. I think the risk could be lessened by greasing the case, as this would slide the case to the recoil shield and lessen any side wall stresses that might come from the case gripping the walls. I would not shoot one of these rounds dry, I would lube the case with case lube, vasoline. In fact, I would probably dip the bullet in a grease similar to what I did with this 45/70 case.
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A secondary reason would be to add as much lube to the tube to keep the fouling soft. An excellent BP lube is 50% crisco, 50% beeswax by the way. I used that on my Minie balls.
Case capacity is greater on the balloon head than the solid head, so the balloon head cases could take 40 grains of BP (I have not verified this with my cases), against 35 grains in the solid head. Which I have verified. Others have chronographed the 40 grain load and it will push a 255 grain bullet close to 1000 fps, which is not chicken feed for a 45 LC. The original Cowboy load was very powerful, and the pressures were low. You can understand why BP Colt SAA's in 45LC were still around to WW2, loaded with BP rounds a BP era Colt SAA would be a powerful weapon. And probably cheap, hard to believe the values now of the things.