I hve a QB79 - its a bolt action single shot CO2 rifle that gets about 600fps. And we get about 30 shots per cannister, no where near 50. If they are stating 50, it is either using less gas each shot (way slower) or it is telling porkies.....
The great thing about the QB79 is you can fit a paint ball cannister underneath for around 500 shots per fill. It looks like a grenade launcher under an old 22 so a bit silly, but it works. You can also use them with a remote tank on a hose same as a paintball gun, which means when you store it you can lock the propellant and the air rifle away separately.
Not sure how easy it will be to find one- probably about $300 but I have not seen one in ages...
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