Girandoni Air Rifle

you'll put your eye out...

Not a bb gun, more like about 40 caliber or some such and capable of killing things.

What's the MV. I've often wondered if there isn't some upper limit on both air rifles and black powder rifles.

I would GUESS that velocity would have been something like 900 - 1000 fps but that's just a guess. Max velocity of black powder weapons was always something like 1200 - 1400 until just recently with inline black powder weapons and 150-grain loads and metal good enough to hold that. Max with those kinds of weapons is probably around 1600 or so. Half of the weight of black powder gets turned into gunk and white smoke while smokeless powder is vanishingly close to 100% efficient, huge difference. The biggest problem with early repeating rifles in Custer's time was barrels gunking up, which was also the main impetus for the multiple barrels on Gatling guns i.e. more shots between cleaning barrels.

An air rifle of course had no such fouling problems. The idea was to have the air cannister in the stock be detachable and guys behind the firing lines in an Austrian army operating donkey turnstyles to recharge cannisters.

The thing failed to make Austria the supreme military power in the world for several reasons. Mainly, they'd have had to totally redo the structure of their military and create a citizen army of some sort with people bright enough to use the things.