Greetings,
It is good to see others taking interest in the PCP=precharged pneumatic air rifle, of Girardoni. My friend Martin Orro and I ,Hank Elwood have made two of these interesting air rifles. Finish date was Dec. 2012 it took Martin and I 4 years to make. The historical opperating pressure was about 850psi. They were able to fire 40 rounds from their precharged flask, but what we found was that if not shot under ideal conditions ie. pumped to their ideal opperating pressure you might not get all forty rounds off. One of the uses for the ramrod with the rifle was to push the ball back to the breech that didn't make it out the barrel. The soldiers carried 2 extra air flasks and 4 extra "speed loaders" making a total of 100 rounds. Check out Dr. Beeman's site it has alot of information.
If you think about it the next succesful breech loading firearm didn't come out until the Spencer about 1860's. Our air flask is smaller in volume that the original ours holds about 650ml of air I think the original was almost a liter. But, even with 650ml you can fire all 20 rounds in the magazine as quickly as you can cycle the breech block. Our rifle shoots a .457 round ball our opperating pressure is 1000psi after 20 shots there was still 530psi the average FPS for all the shots was 529fps. Martin is very good with computers and has made a web site at Orro.net there you can see more details on the 2 we made. I took it to Bowling Green last year. Thank you, Hank