Last week, I introduced a project that demonstrated how a BB machine gun could be made out of a soda bottle using only a handful of readily available parts. If you missed it, you can check out that project here before reading on.
While the first version of this machine gun requires an air compressor to fire, in the following video I will be demonstrating two modifications that do not.
Both modifications made in the above video can be used remotely. The first model requires no powered air supply whatsoever, and is only limited by the user's strength. Many hundreds of shots can be fired before a refill of the pellets is needed. The bottle may eventually wear out, but the cap with the barrel assembly attached can be easily switched over to a new bottle at any time. You even get a free drink out of the deal when you buy a replacement.
The backpack modification does require an air pump of one kind or another to refill. It may still be pressurized using an air compressor, or if not available, a bicycle pump can be a more affordable substitute.