Multi-shot designs?

[jackssmirkingrevenge]

A simple blowgun with a barrel taped to it like so:



With 100 psi and lead pellets will happily penetrate a steel can, like so:

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For a compact high pressure gas supply, you might want to check out CO₂ tyre inflators as used here (and some experimentationof my own), of course you have to buy new CO₂ capsules but there's no pumping involved and the result would be very compact